How sure are you that the 'performance increase' in your system isn't due to the double core condenser in spite of using R-134a? I know a guy locally who recently converted his DeLorean from R-12 to R-134a. He is unhappy with the results. With the R-12 it cooled well, now with the R-134a he says that it barely cools enough in hot weather, but is okay any time else. This guy is also a professional mechanic, SAE certified, etc. Walt Tampa, FL