I have an 04 GTP with the following mods:
1. ZZP canned tune
2. dynomax cat back
3. K&N CAI
4. ZZP MPS (running stock 3.8" size for winter)
5. 180 degree stat

Mods going on once it warms up
1. ZZP headers with catted (will be hollow) DP to 2.5" to match up with Dynomax cat back
2. Breather oil cap
3. Autolite 104... had the NGKs and had misfire, runs great with stock plugs for now
4. 3.6" pulley
5. Aeroforce Interceptor scan gauge

I plan on buyinig the ZZP modified 1.9 rockers and the stage 2 intercooler kit. The stage 2 kit will also require an inlet turn down adaptor, alternator relocation bracket, and cradle spacers.

Just wondering which valve springs you guys would recommend. ZZP states "These work with all stock or aftermarket pushrods, lifters, springs, retainers. They will not work with aftermarket cams. Aftermarket springs are recommended for shift points higher than 6000." Mine is tuned to shift at 6000. However an upgraded timing chain is required with valvesprings rated at over 100lbs. I'm thinking the LS6 90# springs should work fine however it also states that the LS6 springs have a recommended install height of 1.8. Should i just stick with the stock springs?

Also wondering if HPTuner can delete the check engine codes for the missing cat and a 160 degree stat. Does anyone know how much of a difference a 160 degree stat will help battle KR compared to a 180? Will using a 160 have any negative effects on performance?

I believe that with those mods a 3.0" pulley will be the smallest I'll be able to run with only the injectors limiting the pulley pize from that point on. I'll probably run a 3.1", just to be safe. I want this car to last a while and am just looking to add a little horsepower to a street car. Don't want to go the turbo route, love the supercharger sound. Not really planning on dragging it but we'll see. Might end up doing it once or twice to see what it can do once it's finished.

I know there' s a lot of questions in here but any tips or advice would be appreciated. Thanks guys.

sorry to not contribute, but that text is hard to read when its blue

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DIY intake-HV3-3" catless dp-180 tsat-DIY shift kit-murphy custom tune

codes can be removed threw the HP tuner from what I know. I just purchased a tuned PCM- cheaper and easier.

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Why have more money than brains? Cuz RACE CAR :

Yes the codes can removed with a tuner, it would be a really good idea to get a custom tune with your mods. As far as pulley size it is difficult to say, depending on your car and how good your tune is. I wouldn't run anything smaller than a 180 t-stat due to your car not warming up completly and causing your car to run richer than it normal. Also you should be looking into a larger MAF. Cause with those mods you should be hiting the flow ceiling on your current one.

Milestone

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As far as the thermostat goes, my buddy with a cobra (Kenne Bell charged) said he thought the 160 would be fine because that's what all the Kenne Bell's come with and lower temp means lower KR, he doesn't know much about the grand prix though. What about the valve springs? Leave 'em stock or 90#? Also, what would you recommend for the MAF, I don't think i've seen any aftermarket ones.

If an engine is designed for the cooler thermostat, that's one thing. Our aren't. Yeah, we can tune stuff in the fueling to make it not so bad, but the oils need to be up to a certain temp, and a 160* t-stat will NOT get them there. There are aftermarket MAF's on Intense and ZZP.

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One Big Ass Mistake America

As far as springs go I would run 105# springs they can be ran on a stock timing chain.

Milestone

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I just found the 85mm MAF on ZZP. I guess I'll go with the 105# springs. Thanks for all the help guys, I appreciate it.

In order to run that MAF you have to have your car tuned for it, similar to running larger injectors. If not your car will not run properly.

Milestone

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Yeah, I know. If i get HPtuner I should be able to tune it properly though right?

Yes. You'll want one anyways to take advantage of the breathing mods.

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One Big Ass Mistake America

Yeah you can tune it in with Hptuners.

Milestone

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Look for the crow cams 110# springs. they're easy on the valvetrain like 105's but maintain their seat pressure much better (the being said I ran comp 105's for years with no issues, the car is still running with them today.

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'05 WRX STi - COBB Stage 2|Invidia DP|3" Borla XR-1|Coilovers|Camber Plates|Swaybars|Endlinks|Bushings|Braces|Anti Lift Kit|DBA4000s|SS lines|
Sold: 06 Cobalt SS/SC, 99 GTP 245WHP/326 Ft-lbs, 06 R6

Good to know... idk i might just say screw it, take out a personal loan, and go xpz cam, stage 4 heads, double timing chain, stage 2 intercooler, 85mm maf, etc... decisions, decisions

I would never take out a loan to fund car modifications. But that's just me.

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Financing mods isn't a good Idea. I took an extra $1k out on my loan for the scooby (paid cash for the car, took out a small loan to cover tax/title/registtation/other fees, cover soem school stuff and have some money left over), but they extra money only added $12 to my monthly payment so it wasn't a big deal.

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'05 WRX STi - COBB Stage 2|Invidia DP|3" Borla XR-1|Coilovers|Camber Plates|Swaybars|Endlinks|Bushings|Braces|Anti Lift Kit|DBA4000s|SS lines|
Sold: 06 Cobalt SS/SC, 99 GTP 245WHP/326 Ft-lbs, 06 R6

Don't buy and xpz cam, get an xp or s1x cam and call it a day.

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2009.5 SBM G8 GT
November 2011 Car of the Month

Why not? There's people recording crazy numbers with the xpz, 400+whp

-- Sat Apr 09, 2011 3:21 pm --

Would be a lot cheaper though, be able to use stock heads. Although the most you're going to get out of those is like 340whp.

It's a horrible cam to daily drive with. The XP and the S1x are both extremely streetable and you can make good power on them as well.

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'05 WRX STi - COBB Stage 2|Invidia DP|3" Borla XR-1|Coilovers|Camber Plates|Swaybars|Endlinks|Bushings|Braces|Anti Lift Kit|DBA4000s|SS lines|
Sold: 06 Cobalt SS/SC, 99 GTP 245WHP/326 Ft-lbs, 06 R6

yeah if i went with the xpz i'd get a high mpg beater for a daily driver. i'm spendin over $200 a month on gas right now anyway

You get the XPz plan on getting the double roller timing chain (150-200), 150# springs and 130# springs (200), head work and porting (500), shorter pushrods (70), tuning regardless if you have a Hptuner or you pay to dyno tune (350-500). I guess you do the math. What seems a little more logical?

I like my XP cam, headers, intercooler and 3.0 pulley on e85 on 24* of timing.

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Dave's Hocus Pocus Tuning of South Dakota

Go s1x if you're camming, I have a few buddys running them and it works really well.

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2004 Grand Prix GTP
FWI | HP Tuner | 1.9 Rockers | Headers | 3.5 Pulley | 97-03 Control Arms w/GMPP sway bar|

Just wanted to chime in on injectors. I'm running a 3.2 and seeing 130% injector duty cycle and starting to lean out at the top of 2nd gear on stock L32 injectors. If you want to mod anything below a 3.4 I would invest in 42.5's minimum.

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Mods include-
Pulley boys 3.2 pulley, 20* timing, HPTuned, pacesetters, SSIC, modded 1.9's, F/R STBs on Don Rome brackets, 255lph pump, ZZP billet rails, GXP catback
Best of 13.4 at 103.... 12's this year