I'm in the process of rebuilding my a/c system. All new factory components, but on the fence about switching from r12 to 134. I have read that I will need to take the EPR valve out of the compressor suction side because it isn't compatable with the 134. Also need to change the compressor oil. What if anything is this valve replaced with? Seems like something needs to go back in there to regulate the freon flow. If so, what is it?