Sr breaking up...I need help.

[DrtyRat]

I have an s14sr and I'm having a prob. w/it lately. First of it's difficult to start in the morning(I have to give it gas and crank it a few times) and when I hit 3500-4000 rpm @ WOT it starts to break up. I can rev past that point w/no prob as long as I do it w/partial throttle. I boost up to 9lbs and it holds steady as long as I don't floor it, but when I floor it it starts to break up.
The following is a list of things that I've done to try and fix it:
1. Change the spark plugs and gapped them to 30
2. Checked all of the coils to make sure they were getting spark
3. Changed the MAF and cone filter
4. Changed the fuel filter
5. Had it checked for boost/vacuum leaks
6. Checked fuel pump (pump is from a supra tt and was purchased brand new) and the grounds for it
I'm stumped as to what it could be, and I know its one of the common, vague problems, but I'm all out of ideas.
Mods are as follows:
MBC
fmic
blitz nur spec exhaust
test pipe
I doubt the mods are causing the prob. but I figured I'd include it.