try a fuel filter, ud be surprised. most overlooked item with routine maintence. causes hard start and lag at higher rpm

I say check everything the other guys said, then check and re- check the timing. You would be amazed on how bad the Supra runs when something is not set right in your timing. Has you CPS been out of the car? My car had alot of the same stuff going on as your car and after months of messing with it I broke down and spent a couple of hours pulling everything off the motor and re- timing the motor from the begining. Now it runs GREAT hope this helps!