On my Xl I have the following settings: The High speed needle is 1.25 turns in from the groove. 1.5 turns in from the groove is the max lean setting. The Low speed needle is flush with the carb. Flush is the max lean setting. The mixture screw has been adjusted but not much and it's advised to not touch it. The Idle gap is within the rec. spec. You're hobby shop is right because you should not be tuning to a temp gun but however it's very helpful knowing where your temp is at with the settings your running at. So If you're hitting 300 degrees for example with a rich setting, then you would have either one of the two issues: either one of the settings are too lean or you have an air leak. I've ran rc for years without a temp gun and this year was my first full season with one and I don't know how I got by without one. Just remember to adjust your carb with the engine up to temp. Hope this helps, Steve