96 Buick Century Stalling Problem

I've been having a stalling problem with my 96 Buick Century. I never know when it will stall out on me. It happened twice in one day. Once when I stopped at a traffic light and later when I took a turn on to a side street on the way home. It hesitates as I drive and I keep driving hoping that it won't stall out before I get home.

This problem appeared shortly after I had a manifold intake gasket replaced at my local garage and I'm wondering if the mechanic might have done something to cause it such as accidently causing a sensor to malfunction. Also, the check engine soon light goes on and off periodically.

One other thing. The ac compressor needs to be replaced. Don't know if that might be part of the problem.

Any help will be greatly appreciated.

Welcome to AF, get the code/s read and post back.

Here are the codes: PO300,P0336,PO341,PO507