I feel your pain. Its always the same running fine do a few upgrades then it don't bloody work.

Best one I had tuned a mates car 330 bhp all good. Drained the cooling system to fit a 500 cooler and water pipes and then it would never run right. ended putting the old set up in ran fine. Found out later that the map sensor had coolant in it where I drained it out of the header tank. And there a sealed unit go figure.

Got the feed and return pipes correct?

Paul