Running rich....what could go wrong?

[DrtyRat]

OK....I ask this question knowing a few of the obvious answers:
Detonation, fouled sparkplugs, bad gas mileage.
The reason I'm asking is b/c I'm trying to trouble shoot what could be wrong w/my SR. I'll try to keep it short while explain the current prob. Basically, my motor has been difficult to start for sometime, when I cold start it I have to press/pump the gas all the way down for it to start, and once it starts it will idle pretty smoothly, and I was able to get full boost w/no problem. I don't have too much of an issue once it starts. To rectify this prob. I cleaned 1st and then replaced the MAF, fuel filter,cone filter, had the coil packs checked, spark plugs replaced and gapped to 28/29(I don't recall which one, but all are the same), and I replaced the coolant temp. sensor. None of this has helped. After having it like this for some time, I got it started one day, got on it (boost) and a new prob. arose. When I'd be @ WOT and hit 4k rpm it would start breaking up until I let off of it. I can go @ 50% throttle and it will boost and hold w/no prob, although not @ full boost (approx. 5lbs). I've had the car checked for boost leaks and again no problems there. What could it be?
Now back to the original ?...I know I'm running rich b/c my timing has been adjusted to compensate for my atmospheric bov, so that the car doesn't stall. I'm just curious what else could I try to replace on my limited knowledge of cars? I want to know what else could go wrong/get messed up by it running rich. I tried to have my mechanic diagnose the prob. but he doesn't do this full time, just in his very little spare time, and he doesn't have the time to really trouble shoot. If I cant fix it myself I will pay to have a "shop" look at it. I don't mind spending the money to have it done right.
engine/mods...
S14 SR, FMIC, 3" downpipe, 3" test pipe, blitz nur spec exhaust, AEM universal cone filter, cometic hg, arp headstuds, Supra TT fuel pump, and mbc set to only 9lbs, everything else is stock (injector and such)
I forgot to add the my ecu has thrown a code only once,car was sputtering, and wouldn't rev w/o breaking up, and I didn't see what code it was giving off. At the point the CEL came on, I turned off the car, started it again, and it didn't come back on.
Any help would be appreciated...thanks