2004 performance/exhaust

I want to get a few performance mods for my 04 Grand Prix vin 2, what are the most effective ones? I am going to port my exhaust manifolds myself. Can an aftermarket universal high flow cat be installed without significant bending or welding? Also are the universal high flow mufflers from magnaflow fine to use or should I look for a direct fit. I will add the regrogrammed ECM and 180 degree thermostat. Any other suggestions would be awesome. Thanks alot

Definitely go with a re-programmed PCM module. However, you are aware that at least 91 octane or better premium gas is required to get the full benefit.

The most effective exhaust mod is headers however they are not cheap and the install can be a PITA. On the PEM that is a lot of work considering you can get PEMs already ported and polished. See link below.

3800Performance.com (http://www.3800performance.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=PEM&Category_Code=ES_H&Product_Count=2)

On a typical aftermarket hi-flow CAT converter install if we are talking about the converter only welding is required. The input to the CAT from the downpipe should always be welded. Other option is to get an aftermarket downpipe and hi-flow CAT combo to make it a bolt on job. These have the flange needed to bolt up directly to the resonator with no welding. Also the downpipes have bigger diameter tubing. 2.5" - 3.0" for a nominal power gain.

The bottom line is what are the goals on performance and how much you are willing to spend.

I thought the PCM would be the best for the money...I always use high octane fuel so that part is covered.

The only reason I was going to port the PEM myself was to save the $250 and use it for the afermarket universal CAT and High flow mufflers. I do have access to the welding part of the exaust but do not have access any pipe bending equipment, Does anyone know of the best universals to fit this car? I want to stay around $500 for this go around, then next spring get some more aggressive mods.

Once again thanks for your help.

I am also considering eliminating the resonator all together.

I was told by multiple people at different exhaust shops, that, at least on my year GP, that removing the resonator will not increase performance, since it doesn't restricts air. But it will give it a beefier sound.

@BNaylor
Not to hijack the thread, but would you recommended the reprogrammed PCM for a mod setup similar to mines? Also, what exactly is the "40MPH WOT lag"? I have noticed some type of lag when accelerating, and I have to wait a sec or so for my car to "move out".

I was told by multiple people at different exhaust shops, that, at least on my year GP, that removing the resonator will not increase performance, since it doesn't restricts air. But it will give it a beefier sound.

That is true. Really no power increase per se. I don't know about a beefier sound but it does get louder and more raspy sounding. Plus give you a headache from the droning sound on long trips.


@BNaylor
Not to hijack the thread, but would you recommended the reprogrammed PCM for a mod setup similar to mines? Also, what exactly is the "40MPH WOT lag"? I have noticed some type of lag when accelerating, and I have to wait a sec or so for my car to "move out".

Absolutely. Just what it says. It removes the bog or lag feel at that speed by improving the torque management tables. The PCM is programmed to take advantage of any intake or exhaust mods. Most of us feel a difference in the seat of your pants just with a re-programmed PCM.

The other advantages no one really discusses are the improved fan turn on points at around 185 degrees. This cuts down on the engine temperature creep up that you get at certain times of the year when not running the A/C. Plus you can install a 180 or 160 degree thermostat. Also, when you turn ignition to off, the cooling fans will run for approximately 2 minutes which is a good feature.

I am going to keep the resonator... I am thinking I will go with the high flow cat and the universal high flow flowmaster muffler 50 series. I will definately get the reprogrammed PCM.

I was reading that when getting ported exhaust manifolds it is really only necessary to replace the front one, since this is the one that has the most resistance.... Is this ok to do this?

If there are easier or more effective performance mods I would love to hear them. I need to stay around $500-600.

I am looking at the downpipes with high flow cat at ZZP and noticed that they offer different sizes. Would the 3" bolt up to the factory exhaust or do I need to get the 2 1/2? Also what brand PCM wold be the best for vin 2. Thanks

The 3" downpipe is a direct fit bolt on. It will clear the tunnel. Personally I prefer 2.5" exhaust plumbing throughout all the way to the at least the mufflers. Some exhaust back pressure is needed and should be considered when deciding which pipe diameter to go with. But you should have no problems with a 3" downpipe. Stock is 2.25".

For a daily driver and minimal mods the DHP v1.0 is a good all around reprogrammed PCM module.

What is considered minimal mods? I wil not do anything like cams, but I will have the exhaust mods like exhaust manifolds(front), 2.5" (per your suggestion of some backpressure)downpipe w/ highflow cat, high flow mufflers,180 degree thermostat, along with the air intake done within the next 2 weeks, I will also soon put the MSD coils and 8.5 wires within a few months. A little later I will go with the GTP injectors within a year, and high flow fuel filter. This is nothing compared to yours though :( Is the DHP good for these mods or would the intense be a better option.

:meant:

Basic mods aka Stage 1 like intake and exhaust excluding high ratio rockers, cam, headers, polished and ported manifolds or Stage 1/2 cylinder heads, etc.

IMO the DHP PCM is the most time proven and popular one. Even ZZP used to offer DHP until they had a falling out with DHP and decided to offer their own. Little or no issues with the DHP so hard to go wrong. The programming is basically Stage 1. I have a DHP v1.0 in my Regal GS but that is my daily driver and the mods are about as minimal as you can get. In my GTP I use the Intense but it is custom programmed based on my mods. But nothing wrong with the basic Intense PCM either.

Thanks a lot for the help BNaylor!!!!!! I will keep you posted, probably in about 2-3 weeks once all the mods are installed.... Thanks again

Does anyone have an idea of the parts I need to make the fenderwell intake kit? I made one for my 97 but obviously the 04 is a little different. I just wanted to see if anyone had the part list of the top of their head before I buy a bunch of parts I do not need. Thanks