I have the Downey "High Performance" Dynomax Flow Thru but since I regeared to 4.88s the motor just gurgles and I can tell that there isn't enough back pressure. I am also running a Downey smog legal header. Let me nkow what you're having luck with.

Downey header, Holley carb (no it does NOT suck on hills)
2.5" exhaust with a flowmaster. Works very well..

See I'm running the 2.5" exhaust with a Dynomax and it sounds like I don't have enough backpressure and it's causing that weird motor gurgle. I just priced the stocker from Spectre and it's $113 including tailpipe.:eek: Any aftermarket suggestions?

yeah, get a flowmaster..

The muffler that I got with my downey kit was lousy..
So was the tubing actually.
Very thin walled..

i'm running spectre's two piece headers with 2 1/2 in. pipes with a two-in-two out,two chamber flowmaster muffler. it has turn downs right after the rear axle. they clear the flex, sound great, and produced a hell of a lot more hp than the ol' cherry bombs.
Cruiser-B