I just recently had my compressor wiring repaired and lines checked for leaks and the tech at the shop said that i needed to add another pound of freon to my line so i did, now when ever i run the a/c the idle surges and the car even backfired once while it had low idle. also, even though i added the freon the can still doesnt get very cool. has anyone else delt with this issue before and if so what do you recommend?

Thanks