Go the cooler and retune if that's reaching the top end of the power you are looking for. If chasing more, get injectors etc ready to install and do all the changes at once. That way you will not be shelling out for tuning with every change. On the other issue, I stated this before on a number of occasions: It should be mandatory to flash the car back to stock for a day every 2 - 3 weeks. That way, you keep some perspective on the increased performance of the car. Like most of you, the power now feels, er, normal.