After tracking down all vacuum leaks after the cylinder head repair, I was ready for a day of smooth sailing. Right out of the garage, the car shot out like a scalded dog. I was very pleased. However, by the time I was 15 minutes into my journey things got bad. I had no acceleration and eventually would have to shift down to 3rd just to make up the slight inclines on the highway. I tried disconnected the cold start valve on the way home because I thought it might be energized all the time, but I had the same result. I know this problem is temperature related and I'm trying to track down the culprit. It sounds like it might be a CPR problem, although mine is new. Could an incorrectly installed vacuum delay valve create this problem? What else might I look for?