Just replaced my Flowmaster 40's with Moroso's Spiral Flow mufflers. I'm still running the pipes from the American Thunder system (including the H) but dump into turndowns after the new mufflers.

They look like small, fat glass packs so, fitment is great for tight spaces. 4" by 18" total (12" body). There is a low rumble like the Flows but nowhere near as loud. They sound awesome under load: sort of NASCAR-ish. Maybe louder than the Flows under load outside of the car, though. Best part is, they DO NOT resonate inside the car!

The only thing that sucks is they aren't aluminized. I'm going to let them rust a little, then paint them with POR-20 or something.

Though I'd give you guys with Flows looking for replacements some feedback.

Chad

Chad - I'm also happy with mine. Used them because of tight fit (mini-tub, ladder bars). Installed them behind flanged removable X-pipe, 2.5" system. Wondered about backpressure behind my 468, so I adapted a pressure gauge and fitting into O2 sensor bung in collector. From idle to 6000 rpm showed no pressure. Had X-pipe and both mufflers ceramic coated for durability. Sounds great also........DC