If you haven't solved your problem, then it's probably something between the gas tank and injectors. Fuel pump screen could be clogged, regulator might be bad, injectors clogged.
Might even have something to do with the MAP sensor. Even though if you checked it and it was ok, it wouldn't hurt to buy map sensor cleaner and clean it out. CRC makes some cleaning agent. Try spraying some carb cleaner into the tb under load.
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