Im looking for best performance mods- most hp/tq gains (not sound)
After searching and reading through several posts I've come to these conclusion based on g35driver members

Best Exhaust - Fast Intentions

Best Intake - JWT Pop Charger or Stillen Gen 3 Long tube

Best HFC - Fast Intentions

From what I learned on here, some if not most intakes dont give much gains, some even result in losses. Stillen Gen 3 Long tube requires cutting (which Im not willing to do) so I'm leaning with an easy installing JWT
Any input is welcome...

I have the Fast Intentions Exhaust and HFC and certainly noticed a difference when they were installed. I have since went back to a stock HFC due to the noise on the FI HFC. When I removed the FI HFC I certainly noticed a power loss in the Mid and High rpm range.

I have the FI HFC up for sale here.
The FI HFC was on my car less then a week.

The Stillen G3 does not really involve cutting it involves making a hole slightly larger in the mounting brace for the radiator (I believe). I don't think this is a big deal at all. My worry is the filters are exposed and might have issues with water, but so far nothing has been reported. I am going to wait a bit on these, but they are the best so far. R2C is also releasing an intake shortly and that might also be nice, especially their filter design.

From what I have read to this point the stock intakes have been the best for performance, with maybe the exception of adding K&N drop-ins. The Stillen G3 is showing promise it appears.

The FI cat-back seems to easily be the best. I plan on installing this once winter passes and put a down payment already to hold the sale price that is of course now continuing indefinately, no biggie.

Another nice simple mod is grounding wires.

These will likely be my mods this spring. FI cat-back, Stillen or R2C air intake, Black Betty grounding wires and window tint. IMO the HFC will make the car too loud, but likely offers solid performance gains coupled with their cat-back.

I agree with you... I have the following:

Best Exhaust - Fast Intentions

Best Intake - K&N Intake ( I have stillen long tube and JWT on my G, K&N is much better!)

Best HFC - Fast Intentions

Maybe try betty's grounding cables, the auto guys love them... I'm a 6MT and like... though not big diff for me.

For Exhaust if you want something cheap with good results go with a custom made H pipe and Magnaflows for mufflers.

For Intake--- JWT Dual Popchagrers- best thing i have gotten for the car. Makes the exhaust growl just like the G37s but louder. As power goes i felt a gain.. my car has never pulled this hard. I'm guessing the custom exhaust and JWT intake work perfectly together.

How much were you planning to spend?

LOL i was just about to say TT kit!!

This is true as you could go the Turbo route if you want to go nuts. Probably abusive to your car, but its the best performance mod I've heard of for our cars.

looking to spend about 2k the most. I think Im backing away from HFC's at this point. Too loud and bad emissions.
Im probably going to wait to spring too and get FI cat back exhaust.
Intakes...I might just leave stock. I really like the 3G Stillen but i'll wait til I hear more about it. If it doesnt involve cutting like you guys are saying I may go with it. But right now the FI exhaust seems to be a definite

Aren't catbacks louder then hfc's?

Good choice.

(Thrillryder23) Well... HFC w/ cat backs would make too much noise. Im pretty sure the cat backs are louder then an HFC on a stock exhaust

(Chapter29) I wouldnt do turbo if I had the money. My engine will be blown in no time lol

Wikipedia has some good info about aftermarket exhaust and intakes if anyone is interested (I know, not the most reliable source). Pretty much the same topics discussed on this board
http://en.wikipedia.org/wiki/Aftermarket_exhaust
http://en.wikipedia.org/wiki/Cold_air_intake

Good call on the FI catback, I love mine!