I have the FAST EZ EFI 1.0 and I’ve had it since 2012. Ever since I’ve owned it I’ve had an issue with the engine stumbling and sometimes stalling when I push in the clutch and let the engine come down to idle. A few months ago I was advised to adjust the IAC from where I had it set (15-20 per the instructions) down to 05. Once I adjusted it to 05 it seemed to solve my stumbling problem. However, I still have a problem I need some advice. I have my IAC set at 05, but it doesn't always stay at 05. For some reason, after firing it up from a cold start, the IAC runs around 15-20 (once it is warmed up) and then sometime later after driving it for a few miles it will adjust itself and run at 05. When it’s running at 05, it runs perfect, but when it’s running higher then I have problems with the engine stumbling. My question is why is the IAC sometimes running higher than what I have it set at? Do I have a malfunctioning IAC? What’s causing this issue? I'm tempted to buy a new IAC, but I don't want to spend + or - $100 for nothing and it doesn't solve the problem. So I thought I'd get some expert advice first. Thanks for your help.