They are in the same price range (SRT intake vs. PPE headers), which is a better first mod on an otherwise stock GS400? Looks like the SRT provides a bigger bump in power, but what about real world experiences?

 

if you are gonna increase the flow in, you must increase the flow out.

 

SRT will be a better first mod and will work in conjunction with the headers. You can do the headers first but you can only flow as much as you bring in as mentioned above. The headers are also a much longer install. If you want to mod I would personally do it in this order:

1. SRT Intake
2. Cat-back Exhaust
3. Headers
4. Torque Converter (This could be moved to number 3 if you are looking for considerably faster timeslips) Don't forget a tranny cooler when you do the TC.

I'm sure some other people will chime in, Rock-A-Lex (Sp?) has a 400 I think and has done a lot of experimenting with mods, he's be a good guy to talk to. I think he is actually in Philly or New York as well,,,,hit him up, he's a good guy.

 

Are the intakes really that restrictive on the GS4's?

 

not really but the headers are no doubt.

 

The factory intakes use a more restrictive filter element as well as a convoluted pipe. The reason the SRT makes more power is because it is a larger diameter pipe, it's smoother on the inside (air flows better) and it also adjusts your fuel delivery (that's what the SRT ecu does) to make the most of the extra air that's coming in.

Headers are a good mod but for the money/install I think you would be better off doing the intake first. Putting the headers in isn't really going to allow you to bring in any more air than you already are as the factory intake is sized for factory air flow needs, not a motor with headers etc... The headers however will help get rid of the additional air the SRT intake provides. Doing the headers first is kind of like skipping to step 2 or 3 instead of doing the stuff to support the headers first. Hope that makes a bit of sense.

 

Who makes headers for the GS4's? My concern is messing up factory reliability with poor quality parts.

Likely not do anything like headers, not right away at least.

I read the GS430's have larger pipe than the GS400's, is a GS430 exhaust on the GS400 worth it, or not worth the hassle for the bang for the buck?

 

best bang = get da NOSSS

serious.

 

Not on my daily driver!

Where can I find out about ECM tuning? I do GM ECM/PCM tuning now. I want to tune the GS. Is it piggyback only or is there a real PCM tuning solution?

 

For sure SRT intake first. If anything, headers can even go after a catback exhaust like stated above.

 

The Srt is a piggyback, it is pre-tuned and not user adjustable. You can either go to Srt and have it customer tuned for you car or get an accurate dump with A/F and Mo can tune it from that. You can do an apex'i afc instead of the srt ecu if you want to be able to adjust it yourself but the Srt isn't sold without the ecu so it would be a bit more expensive, especially when you consider the needed dyno time after that to tune it.

 

im with you on this....... headers, catback, intake and nitrous. do it all at once!!!!

i had a sc400 with intake, full exhaust and nitrous. ***** moved!!!!

 

I wouldn't even bother with headers on the 400

 

LOL... yea, 21whp and 17lbs of torque? who needs it...

 

i know huh/

http://www.ppeengineering-onlinestor...&categoryId=32