The pressure will rise and fall as the a/c operates. You should have very effective a/c, mine is, after finding the leak and fixing it! You might have a system leak, check for that. I had the service valve (where you put in the R134) fail to seat, you could see bubbles in the valve hole. The compressor should not cycle on an 80 degree day. Clean the IAC, for sure, if the rpms fluctuate too much when a/c is on or quick steering is done.
