I did a y8 head swap on my y7 not it has a jumping idle on start up going all the way to 5k and back down. Found leaks in coolant lines then got all the bubbles out but still jumping. I also have a straight pipe exhaust. Do I need a new ECU or could it be sensors or possibly still leaks?

 

No you do not need a new ecu. Might want to clean out the IACV sensor for starters and see if it helps also the FITV I believe can also cause this as well as a bad MAP. I do not believe a vacuum leak would cause the surging the car would either be running rich or lean. I just put a fuel pump in a corolla and although new pump the car is surging up and down and the fuel pressure is steady and well within specs 44 psi go figure.