S14 SR20 help! Over fueling

[808_silvia]

Well I've done lots of searching and trouble shooting for months now and can't seem to get this car running smoothly again.
I have freshly rebuilt the top end of my sr20.
List of upgrades after rebuild:
S14 sr20det
Hks step 1 256 cams
740cc injectors
Z32 maf
Rs enthalpy tune

I can't figure out what else is wrong so please help me on this one. Car idles normally but sounds like its missing a couple times a minute. When I go to rev the car, it sounds like it being over flooded with gas. But if I keep revving it, the excess gas seems to get burned out and I can rev the car like its running perfectly. But once I let it go back to idle and try revving it again, it starts to bog again. Spark plugs are fouled and black smoke coming out the exhaust.

List of things I have checked:
Compression- 150psi across all four
Timing- set to 15*
Checked for vacuum and boost leaks
Changed out mafs with another z32
Maf wiring should be correct and I can rev it throughout the whole rev range

Last thing to check is the injector o-rings.
Would leaking o-rings cause this though? The car starts up fine and idles nicely, just has a hard time revving it up. Martin at enthalpy has been helping me out a lot but I need to get this car running asap. It ran perfectly before the rebuild but after is when all of this started happening.

PLEASE HELP, this is my daily