Today I decided to hook my uncle's set of R134a gauges up to the sub. With the A/C on full blast, max a/c, and the temperature lever as cold as it goes, I was reading around 25psi on the low side and around 158-160psi on the high side when the compressor kicked in. I'm trying to figure out if the freon is at the optimal charging so that I can get the sub as cold as I can. The A/C from the factory has rear air, however, the previous owner of the truck had the rear a/c lines capped off at the T-points in the freon lines in the engine compartment, so as of this moment, I'm running the front a/c only. So, can the A/C do better than it is already? I've looked a little on google for help, but what I've found doesn't seem to be very clear and concise. It all seems to think you have a decent understanding of A/C servicing. Any help is greatly aprreciated in this hot New Orleans weather.