I wouldn't have thought it was a software issue.
I think you just need a more methodical approach to your testing, start with the basics and work through.
I am guessing when it gets to the sweet spot of 2500rpm it's detecting a missfire and switching off the injector for that particular cylinder, have you confirmed this and which cylinder is missing when it returns to idle??

There are many tests to be performed here, using a scope or live data, looking at lambda and map readings, you can monitor anything while increasing the revs, if you've got a scope, stick it in everything, use a long time base, then you can zoom and scroll back .

Don't forget basics, fuel pressure flow, engine vacuum with gauge for overall mechanical condition.

Chris