I'm confused with the responses of various posts. I was thinking of going with the Stillen cat back because most of what I've read state they have the largest HP gains. However, I've seen a few posts here with comments that the muffler (exhaust sys) is more for sound than HP gain.
I just picked up my '05 G35 5AT, Sport tuned Pkg, Nav, Prem Pkg, and Aero kit with splash guards & front chin lip (chrome 19" I-Forged wheels come next week). I'm getting back into the "game" as I have not had a toy car since I sold my last 5.0 Mustang 10 years ago. As such, I want to make some improvements over stock but I don't want noise level alot of the longer guys are pushing for. I've already put on a Weapon-R secret intake and want to finish it off (for now) with the exhaust.
My question is, do you think I would be better off saving a buck and going with a Borla cat back vs Stillen? What if I added high flo Cats to the Borla will I get larger HP gain vs Stillen cat back?
Thanks in advance for teaching an old guy new tricks!

 

The biggest bottleneck in the exhaust is the double chamber cats. So, IMO, if you have a choice between an exhaust system or Hi-Flow Cats. I'd take the cats. But, I'd do intake mods and an exhaust also.

As for being old, you wont catch me, I'm 66 and having a ball mith my slightly modded '03 6MT.

Lou

 

hop over to the exhaust section... myself and others have posted comments on an irratating sound at 2k-2.5k so far borla and injen have been reported , im sure others as well . I believe its called a "drone sound". anyways its more pronounced on auto since they live in 2k alot.

grab the cats first then decide on the other stuff. cant give any recommendations as to which exhaust to get or which cat backs.

if im reading your question right...

best performance as follows...

cat back w/ borla will provide better performance gains over just Stillen Cat back.

ppp

 

cats > muffler

actually, get rid of both

 

Ski35....

I am much like you, (same car too)

I don't want the noise, nor do I want the lacking low end

Given that, the High Flow cats appear the thing to do.
I will be adding those in a few week.

Over all, and like me given it's an AT....

- Get a Grounding Kit (GroundingGear appears to be the best - mine on the way)
This apparently offers much smoother and FASTER shifting with the AT
- Get a Plenum Spacer From Hydrazine(MotorDyne) lots of gain for a couple hundred
- Get the high flow cats (I am pretty much settled on Crawford)
- At a minimum - replace the paper air filter with a K&N
( I am also getting a stillen high flow, and will play with it, and also am looking at modifing the stock air box. (I'll let you know what I find)
- When it becomes available - look into a technosquare ECU upgrade

all of these together can be done for under $1500, and should yield a good 30 HP

On another point, you, Lowrider and I should start an 'Old Guys' sections

(I am 46 goin on 15)