I say call up Xtreme Flow Exhaust Research & Delelopment and talk to them. I did and that's what totally sold me. They flow better than Random and cost half as much also. It's up to you what you put on your car and everyone thinks something else is better. I like Xtreme Flow and have had no problems in the past 6 months since putting mine on. I did notice a big difference when I installed mine. Gas mileage went up to which was great. Good luck with what ever you decide to buy though.

 

About the LS1. I had a Pontiac Formula a year or so ago. They use the same engines as Vette do but the HP is about 30 to 40 less. It's because the Camaro's a Firebirds exhaust and intake is much more restrictive than the Vettes. When I opened up my intake and exhaust oh my god what a difference. On a 5.7L it's easy to get gains like that. A cat could easily give you that 7 or 8 HP. On our smaller liter engines it alot harder as you all know.

That's just my 2 cents.

 

Yea my last car was a Z28 so I know about them too. The cat didn't make THAT much of a difference, but if you say they're good, then I trust ya

 

Catback system shows a 6.1 HP increase on an auto. Thats on a 1st gen tib with no 2nd cat under the car. So with a highflow cat and a catback on a 2nd gen your should get at least 5hp. 6-7 on a 5spd....
-Steve