ive got a 393 stroker, f cam, windsor jr world products heads, edelbrock performer intake, and everyone told me i needed 42's so i went 42's. i cant get it to idle worth a crap, cant get it to not stumble throughout the rpm range, i lowered my fuel pressure to 37psi, have checked everything atleast 3 times and im still getting way to much fuel! unless you are going to have it tuned to have the injector cycles lowered id go 30's if i were you. bigger isnt always better.
check your timing if your headers are glowing, if you timing reads right and the headers are still glowing then maybe you should check your balancer to see if maybe the elastomeric material is bad and the balancer isnt reading right.
did you put the motor together? maybe it has an aftermarket timing set and whoever installed it retarded it??
No offense, but you have something wrong with your tune brother. You can't just swap injectors without retuning and/or getting the MAF recalibrated.