My Celica just turns itself off

I have an automatic 2000 Toyota Celica GT with DOHC engine. My check engine was stating miss fire on 3 and systems too lean. So we changed the coils and spark plugs then my car didn’t want to run at all kept shutting off. Took it to a mechanic changed throttle position sensor, the computer, 1 fuel ingitor, crankshaft sensor, a relay that controls fuel and the computer, and cam sensor. Now my car runs great until it warms up. Once it warms up the car shuts off and will not restart until the engine is cool again. Mechanic told us fuel ingitors not working once car warms up. The mechanic took the car to Toyota and they can’t even find the problem and the car has been in the shop over 2 months.