My car seems to run like crap unless i have some addative to the gas (spiting and sputtering) without addatives it feels as if it is misfiring, but I have no misfire codes coming up. I have 106,000 on it and havent replaced the coil packs before. The dealership said it sounds like injectors since it runs good with addatives but without it spits at high rpms. Is there a way to check injectors or maybee even the coil packs? or should I have them do their power flush on the injectors. does it realy work?