I don't think it smart to waste the money on muffler only get a 3 inch. I mean 3 inch is a better imho. Flows better, you car needs to breather with a cold air kit and catback it really can make her breather above the 4500 rmp bottleneck of the lt1 stock system.

 

Well, I got the car dynoed.

http://community.webshots.com/album/155792296dfzHRT

278rwhp 310 rwtq


Thats compared to this guy, this guy and this guy. All of which have 3 inch exhausts, some high flow cats. My cat is a stock Meineke replacement cat.

I also found this dyno sheet in which the guy used a cut out. I'm interested to see what mine would do with an offroad pipe and cut out. I may be able to reach 290 like that..

From what I can tell, the stock I pipe is fine for bolt ons but to each his own. If you plan on doing a cam or something else extreme, or just tuning eveyr last bit of power out of your system, a full catback may be for you. The muffler seems to be working for me.

 

IMO, I think a cat-back it worth with a muffler system 5-8 due to bigger exhaust piping, now with a Loudmouth with know muffler I pick up 15RWHP with stock exhaust manifolds cats and y-pipe. If I had the money to burn and didn't like the Loudmoth I would buy a high end cat-back GMMG(NICE!) Borla and so on... If my $$$ was tight I would replace my factory muffler with a spintech which IMO flows more the flowmaster and gives as good as sound and will still pick up ponies. and maybe change out your tips.

 

The stock muffler is by far the majority of the restriction in the stock cat-back. The stock intermediate pipe is 2.75" OD NOT 2.5. It is mandrel bent. The stock tailpipes are 2.5" in OD mandrel bent. If you want the most bang for the buck, you can replace the muffler alone and that will give you nearly all the gain of a full cat-back on most stock or lightly modified cars. When you get to high horsepower, moving to 3" pipe is good, and only for very high powered engines is 3.5" or larger pipe needed.