FR=Smile

Ive got an s13 blacktop in my 93 240 and lately the engine has been running weird. I bought the car for 1500 bucks online so im not sure of its history but here the problem. Some of the time the engine runs smoothly and boosts the same but it irratically starts misfiring and running strange at above 4k rpms sometimes. Ive had a local tuning shop check it out and the ignitor chip and coilpacks are fine, that mechanic said it sounds like a sticky injector on number 4. So i got some bg44k and am running it through the tank now, and it seems to help. However the wiring on the car is pretty sloppy and i dont know if an ungrounded wire or a short could be causing the problems.Another theory i have is that it may be caused my a wacky MAF or overburdened fuel pump. I know the fuel pump is stock and the MAF is from an 89 240. my guess is that the car has around 240-250 hp. And i dont know what that MAF can flow to, or how strained the fuel pump is. Thanks for any input