Mine ran a bit shitty once because the reed petals weren't seating well, they were aftermarket ones at the time. I swapped them for a good set of original ones and noticed a great improvement because more fuel was staying in the engine at low revs...
as for the very loud DEP, well it shouldn't be that loud...again I had an aftermarket can that I had re-packed using the loose fibres they sell, trouble is it packs so solid that it loses much of it's ability to actually silence and affects performance badly...now I always use the matting, its much more airy if you like, sounds better and performs better too.