Engine stalls with noise under dash

My 98 Tacoma has a fast clicking or buzzing sound behind the dash while driving. It is very intermittent and comes without warning. Worse, the engine stalls when the noise occurs and I have to rev the engine to keep it going in traffic. I had a mechanic check it, but he could never replicate the noise and the diagnostics didn't show a problem. It happens both while waiting at intersections as well as in motion. It seems like the noise is on the driver's side. I've read plenty of threads on problems with the A/C servo motor, but that is on the passenger side and shouldn't stall the engine. Could it be some sort of short in the ignition switch wiring?

 

New ignition switch is $76 at autozone - could be worth switching it out.

 

Fuel cutoff relay.