will this be enough?

[Shift_450R]

i have a 03 400EX and i put on a white bros e series slip on and a uni filter with a 155 main jet. it backfires quite a bit on decel and it hiccups in the first two gears. if i adjust the fuel screw will it make it better. I think its lean.

[300exOH]

Adjusting the fuel screw should help. If not you can go up to a 40 or 42 pilot jet. Usually backfiring on decel is a sign of a lean condition in the pilot circuit.