I just recently installed my bassani o/r x and ever since I have, when I downshift, or rev in neutral up past about 2500~3000 RPM I get backfiring. Especially if I downshift and the revs go up to about 3000 it sounds like a gun going off, why is this??? Does it have something to do with the lack of cats?

. Second, I know you said you just did your timing and all of that wonderful stuff last week, but find a light and check the timing anyways. Unless your O2s aren't hooked up right it's the only thing I can come up with.