Backfiring is timing. I would set your timing, get a timing light and set it right. The Webers like 4 to 5 lbs of fuel pressure, a regulator does that. I know they prefer the holley FPR, I can't remember what model it is, someone else can chime in, Factory is 7lbs of fuel coming in. Check your fuel filter as well or just go new.
85' CJ7 Laredo, 383 GM, Turbo 350, NP 203. SOA, 2" frame lift, 34" TSL swampers, Dana 30 open, AMC 20 w/ detroit locker, 4:10's, 1 Piece Mosers, 35" boggers to abuse when needed.