I've got mandrel bent 2.25" piping, with resonator, going through a straight-through generic muffler. Whenever I downshift and just let the car slow itself down, my exhaust always starts sputtering exactly at 2500 RPM and below. I can give it gas until just above that point and it's fine. It does this in all gears. It's not that bad, but why does it happen and why at exactly 2500 RPM or below?

mine does it too. but i dont think its a bad thing! i think its because of the drop in back pressure, not very much exhaust gases are coming out under 2500rpm.

myspace.com/coastiecobb

Mine does it too.

Green 95 GS 5-speed
Engine--PCP cold air intake,Greddy header,Accel 8mm wires,OBX custom exhuast.

Suspension/Brakes--Sprint 2' springs, KYB Gr2's, EBC Red Stuff pads,17" Konig Traffiks (silver), 215/45/17 Yokohama AVS ES100's, 15 dollar camber kit.