my friend put just a muffler on his dx, and ran the same track times within a tolerance of .1 (due to driving)

i put on a full catback with 2 1/2 inch piping, and got almost half a second consistantly(same exact 60 ft) and gained 5 mph in the trap speed.

as for sounds, his is def loud but is sounds high pitched like a pissed off bee, where mine is deeper/throatier and a LOT louder.

i haev the apexi n1 and he has an obx muffler that looks a lot like the n1