What size is the Stock Int. Pipe on '89 IROC 305 TBI? I was thinking that it was 2.5". But then Jeg's is showing that the Flowmaster 80 series for my car needs the 3" input. I am not near my car today but I wanted to get an 80 series muffler online today. I think this info is incorrect, but I wanted to see if someone here could confirm it: http://www.jegs.com/cgi-bin/ncommerc...08&prmenbr=361 I think I need the 42583, but you wouldn't think so by looking at Jeg's site. Can someone help with this? Thanks, Andy

Camaro/Firebird Replacements
Add 30hp, 40ft. lbs.!
Single inlet with dual outlets for a stock dual exhaust appearance and fits in the stock crossflow position.

389-42583 1982-85 Camaro Z28/Firebird Trans Am: 80 Series, 2.5''In/2.5'' Dual Out - 80 Series | View Product $72.99

389-43083 1986-99 Camaro/Firebird: 80 Series, 3''In/2.5 Dual Out - 80 Series $79.99

i know my 5.7 iroc-z had a 3 inch i-pipe. so most likely the 305 tbi would have the 2.5.

Stock I pipe on a 305 tbi is 2 1/4 inch non mandrel bent. Get that crap out of there and get at least 2 1/2 inch mandrel bent pipes if you're doing the exhaust.

The stock I pipe on an auto TPI or TBI motor should be 2.5"

IROC TPI and 5.7 TPI all have 3" inlet and dual 2.5" outlets

tbi Irocs have 2 1/4" pipes. Trust me on this, I helped put exhaust on my buddies 88 tbi iroc a couple months ago. Also no third gens ever had 3"I pipes. The 350 and 305 tpi dual cat cars had 2 3/4" pipes.