It will backfire because it's lean, and the performance filter makes it more lean.  Different main jetting won't affect your mixture on over-run, that's down to the idle mixture screw.

Have you removed the brass plug that covers your idle mixture screw?

If not, remove it and open up your idle mix a quarter turn at a time until it stops backfiring.  (If it's still doing it and the mixture screw is 3 full turns out from fully closed, you need a bigger idle jet, but that's not likely).

Have you done the spacer mod as well as the jet?