There are many things that could cause your problem. I will list the easily items to look at first before you spend more money on this. They are bad gas, dirty injectors, clogged fuel filter, and too lean of air fuel mixture. I have particularly good luck with Redline injector cleaner - put a whole bottle in the tank the first time you use them will fix both the bad gas in the tank and clean your injectors at the same time. Have you mechanic run a CO reading to determine if the air fuel ratio is too lean. If the CO reading is way below your state emission limits, have your mechanic richen it to see if it smooth your idle (it did on mine). Good luck.