Flowmaster sucks bad, and shouldn't be on any camaro. Cut-out stock muffler> Cut-out Blowmaster.


That said running with it open will for sure make more power. We are not internet dyno's, so you will have to find out how much it makes on your setup.

 

That's what I did when I was cam/bolt-ons only. Worked great for years, drove around everywhere with the cut-out open. Not one cop seemed to care.

IMO a catback is the single biggest waste of money on our cars. A stock catback with a cut-out is just as good as any catback. It would be nice if more people knew that and didn't blow money on a catback that can be put to better use in other places. I'd still be running mine if I didn't get weight crazy, I now have LT's with bullets welded on.

 

I think it depends on your priorities. I would never want to drive around all the time with the cutout open, and the stock exhaust is way too quiet for my taste.

 

I pushed 800HP through a FlowMaster Series 30 4" single in/single out, part of the highly regarded Mufflex 4" catback. Buddy of mine pushed 1,125HP through the same system on his 30th SS convertible (9.04@156MPH). When they removed the 4" Mufflex/Flowmaster, and went to Borla XR1's on the collectors with turndowns, the dyno showed no change in rwHP.

You really can't generalize about a company that makes numerous types and models of mufflers.

 

went 13.5 with cutout closed and 13.2 with cutout open

those times are with a untuned hotcam, the dyno graph below is with 1.6rr, shorties, moroso cai, free mods etc etc