Northstar Engines and System Technical Discussion Discussion, Flowmasters on a 2003 SLS in Cadillac Engine Technical Discussion; Hey what's up guys? I'm looking at flows for the Seville but not sure witch one is needed to fit ...
You need 2 single in/single out mufflers. Depending on size, you'll probably want both inlet and outlet offset. Size, I'm not sure. Measure the pipes before/after your mufflers (assuming you're not going with a full, custom cat back system).
I feel like a friend told me the 40's series were very loud and droned quite a bit. I would take a listen at a few before putting them on. A buddy put a certain type of Flowmaster (can't remember what model) on his Trailblazer and it sounded like shit. Loud, obnoxious and it droned down the highway really badly. He ended up putting a different model of Flowmaster on it that was much quieter. I can ask him when he is off work.
As MC posted - measure and measure again using outside calipers. The roll bending reduces the Y-pipe diameter to almost 1 5/8" in places.
Our original exhaust systems leave a LOT to be desired - here's an example of the pipe roll bending and restriction at the small Y-splitter for the phony duals. (Actually, the "Y" is almost like a small diameter T !) This is the factory original system which was replaced by the CORSA in 2006. The CORSA still looks brand new - 100% perfectly satisfied, and there are before and after dyno runs by a CF member posted here in CF that prove a ~16 hp increase up near WOT redline (for the STS).