Originally Posted by SteveP

This is why we say, NEVER tune to the temp gauge. Tune it for performance and CHECK the temp.

Leave the shimming alone for now. Reducing head clearance requires that you be more skilled at engine tuning, or you may cause detonation, which is going to smoke your engine (as in kill it). I only recommend adjusting head clearance for people that can get the tune right 10 out of 10 times.