I have a 4150 style Holley throttle body on my LS3 with early GM (24 pin) ECU. I've been experiencing a "intermittent" high idle anywhere from 1500 to 2000 RPM and lasting for up to one minute before settling back to a normal 800 RPM. I have no fault codes and engine runs great. My throttle return seems to be fine and it definitely seems like it's computer controlled. I'm wondering if my IAC is not working correctly all the time. I'm wondering how I can check it myself, AND, if anyone can suggest looking elsewhere for the problem? Sometimes I wonder if my GM ECU is talking the same language to my Holley components. Any advice is appreciated. Thank you!