I had dual cats into a 3 1/2" Mufflex with single Spintech muffler and single pipe exhaust exit. All behind a 97ss LT1 383ci D1 with many mods. The cats (Random Tech) were good flowing, but were blown out with all the D1 flow. I started to experiment. Installed (2) 2 1/2" straight sections in place of cats. Good flow, but, lots of noise thru the Spintech. Resonance was a problem @ 2K rpm. I added a CCI insert (3 1/2" 3 disc), and a 3 1/2" QTP dump for full flow open. Inserts are small and easy installed if you have a MIG welder and cut off grinder/ saw. Now, sound level is livable. My experience... flow is always a problem with chambered mufflers, and, sound is excessive with straight thru type mufflers. B.

 

So how the heck do you get through the California CARB emmision and noise tests?
Just curious.

97WS6

 

Un bolt the y-pipe and cut off the exhaust system yourself and put on a cat-back system.

 

The OP (tnmotown) had not been active on the site since October 09. Hopefully he figured out the answer about a year ago.....

 

hahaha, funny you mention that. I actually sold my '94z28 with the 383. I now have a g5x3 cammed '01 z28 with 150 shot. My exhaust is routed the same way!!!! lol. Instead of the spintech muffler, I have a 1 chamber flowmaster. Sounds badass and I dont care about noise anymore because live in a house now.

I did however put a hooker cb on the old 383 lt1 and helped out a little. Still loud though at WOT. Sorry I havent been active on the site though, I need to visit more often even though I have a ls1