If I got a downpipe and testpipe at 3 inch and leave the stock cat back exhaust, will this increase back pressure on the turbo or have other adverse effects since the piping will go from 3 inch to more restrictive stock exhaust piping? I want to keep my stock cat back to look more stock for reasons. But i wanna open up the exhaust soi can make more power. Also wanna keep it quite

 

the two biggest restrictions in OEM exhaust are the muffler, and the cat.
you've kept one of them, so you are not as free flowing as you could be
backpressure is not a bad thing
if you want better gains, you need to address the muffler. Magnaflo, HKS, both make stock looking mufflers. You can also us a Magnaflow muffler from 1999 Camero (i believe that's the year) that flows 600cfm and sets right in there.

 

Thanks for the perfect answer. Will the car be that much louder without the stock muffler though?

 

The car is going to be much louder based upon which CAT/CBE you go with. Might I suggest the ETS V2 CBE. Here is a clip of mine with just a CBE, stock DP and CAT.

 

You could go with the ETS V2 Quiet. Stock look, better flow, and not super loud.

 

+1 I have the ets quiet cbe and the sound is perfect.. low during normal driving but loud when your going WOT.. There's barely any drone.

 

I have the buschur racing quite cat back. It still had a little drone on it, so I took it to RRE and had a resonator installed. Perfect on the freeway and it still sounds good at wot.

 

Get the AMS exhaust. It's super quiet

 

Magnaflow is extremely close to stock. I'm might go with greddy evo 3 which sounds super non existent.

 

Is the Magnaflow a glass-pack or does it have baffles?

 

I believe the T1R 76S exhaust is the quietest exhaust out there. Every review that I've seen says it's barely louder than stock during normal driving and has a nice growl to it when you get on the gas. It's something to consider. There are threads on this forum if you do a search. Or do a Google or YouTube search and watch some of the videos.

Here's a video example that might help:

 

ETS V2 Quiet is still louder than stock, if you're trying to minimize sound. If you add in a TP or HFC, it gets even louder (a "throatier" growl, you may also get pops).

 

I have heard the RRE exhuast in person. It's super quite with indavidual mufflers.
The only bad thing is that you need to drive to them to get it done.

 

If you are wanting to keep the stock cat back and doing a test pipe/down pipe that will indeed work. It won't mess up backpressure or anything, it will still be a little less than originally. If you do get a catback there is only one I would recommend. T1R 76s... this is coming from someone who has had 3 different exhausts.

 

If your not doing a Catback, I wouldn't mess with any of the downpipes. These cars are a little touchy when messing with downpipes.