After a long period of starting and running beautifully my MR2 Turbo suddenly developed starting problems. The engine starts without difficulty but stammers and back fires for 3 to 5 minutes gradually improving until it will run up to the rev limit without difficulty. The engine will start and run well for the rest of the day. I have just spent $600 to have the engine tuned but after a couple of weeks the problem reappeared. Any suggestions as to what is the cause of the problem.

Too many simple things come to mind... Dirty throttle body, timing, dirty fuel filter, poor fuel quality, spark components/plugs need replacing, dirty intake (engine upper spray) fuel injectors need servicing... sounds like a simple service item... they should have picked up on some of the above when being “tuned”