First thanks for any help you can give. Here is my set-up I have an LE1 port job done with a 306 cam, all bolt ons, and a forged motor. I plan on putting 150 shot of nitrous on top of that in time. So I'm assuming right now I am close to 450 flywheel horsepower without nitrous.

I was thinking of using 2 1/2 or 3 inch duals but wasn't sure if I chose 2 1/2 inch if it would be to small for the nitrous and if I chose the 3 inch if it would be to big for just N/A? Also when I hear people say 3 inch duals are you usually talking inside or outside diameter? Also when we talk about true duals I see some people not taking it all the way past the axle would this hurt or help performance? How far back would your recommend me taking the true duals?

Last question, is the pacesetter longtubes collector point 3 inch 'Outside' diameter?

 

There is no such thing as too big exhaust, at least once you get past the collectors. Size it for the nitrous - nitrous needs BIG exhaust. Length of the system is also relatively unimportant. Length does not help or hurt, if its the correct size system. I'd run the 3" duals with your system.

The important thing in exhaust design is the primary tubes and the collectors. Beyond that, it becomes much more an issue of getting the exhaust dumped where you want it, without putting any uneccesary restrictions in the system.

I run AS&M headers, modified to dump straight back so I can run duals. I have a short extension to get the collectors under the body, a Borla XR1 shorty bolted to the extension, and a 3" pipe with a turndown in front of the rear axle. We've tested the car with a full catback exhaust (custom 3" Y-pipe into a 4" Mufflex), the 3" short pipes to the rear axle, and with only the Borlas on the collectors, and there is no significant difference in HP. I'm running 500 flywheel NA + a 300-dry shot.

http://www.injuneer.com/images/photo.../DCP03675a.jpg

 

 

300 shot? wow.. jelous.