My 09 G37x needs a new exhaust system since its rusted out. Does anyone have any suggestions on which specifically to purchase I'm going to buy it online then have my mechanic install it. Also do you think custom exhaust systems are worth it? Thanks

 

Starting with your last question first: a custom exhaust won't add any performance to your G unless you spend the $$ to retune it. If you need to replace the exhaust I can only go with what I've used in the past. A single outlet exhaust is the lightest, but noisy. A true dual exhaust like the Stillen is what I prefer for the street, with a good note and rips only at higher RPMs.

 

Aftermarket exhausts certainly can free up some HP without a tune. The compromise is always a louder car.

However, (for the OP) gains are not aggregated. If you install a pair of HFC with claims of 10hp gains, and a CAI with claims of 10hp, and a catback with claims of 10hp, you won't see a 30hp bump. It doesn't work that way. If you want to maximize efficiency and power, plan on getting tuned and be grateful for 8 to 10% overall.

If all you want to do is replace your corroded OEM exhaust with a new aftermarket cat-back, like Stillen, then you'll likely experience a little extra grunt.

The Stillen catback is not "true dual". Exhaust from both banks merge into an x-pipe design before splitting off into separate resonators and mufflers. There's a reason for this, having to do with mitigating the resonance from the exhaust pulse, or something to that effect.

 

Specifically which portion is rusted out? Y-Pipe off the catalytic converters is normally where I see people complaining about rust.

Agree that the Stillen Cat back is the way to go if the mid-pipe and axle-back portions are also rusted. It will set you back about $1400, but is dyno'd at 19hp to the wheels.

https://stillen.com/products/2009-20...-system-504377