backfires thru throttle body

my 1.0 has been runnig great since the motor change. last nit e it started spitting/backfiring thrugh injector but only under load. any ideas what it might be. no trouble code have registered yet so any help would be great

It is typical thing for those cars to need vavles done after 80 grand. I would put a vacum gauge on it and post your readings

motor only has 30k

check your distributor cap and rotor, cap seems prone to arc tracking

timing,!!!