Honestly, at this point, I'd make it the mechanic's problem. The root cause is something that was altered during the last A/C service, if it ran well before, and hasn't run well since.
I seriously doubt your fuel filter is the problem. I've pulled 25+ year old filters off of perfectly running engines that were full of dirt. Ditto the pump filter. I'm not saying these shouldn't be clean, only that the fuel system is amazing reliable. Besides, I'd rather have a root canal...