fuel problems

Ok so ive posted a few times on here. Its a 1996 GT PI swapped. Motor has been in for almost a year. Around 4k-4500 RPM i get a miss. Plugs, wires, coil packs, fuel filter and didnt change my problem. Did a pressure test on the fuel pump and i was 10 Psi low so i swapped out the pump for a walbro 255. took it out for a ride and still doing it...not as bad but still there. So im thinking its an injector or regulator? I did find a loose connection on one injector and just ordered a new one and will put it on tomorrow. any input would be cool...if the loose connecton doesnt help i have a extra set of stock injectors that ill put in for now or im gonna go with a new regulator

PI motor with all bolt ons....im in the market for either a procharger or an S-trim after i get the bug out of my car and theres no point putting a stock pump back in it if im gonna be boosting it soon. And yes i know there are other issues....from the people i talked to they thought the low psi was the cause of the missing at high rpm.....the only other things i have in mind it to swap out injectors and regulator...ive been checkin for vacum leaks and havent came across anything so far