The first thing I would check is the idle mixture setting. Be sure the rpm rises a little as the mix is pulled on shutdown.
Do you have popping on final in the exhaust too?
Why mixture?? Because at idle on final, you can have a misfire due to mixture variance. You won't feel it as the power level is so low. Burn rate in the cylinder is very dependent on mix and if it is at one end or the other (A/F wise) it can burn really really slow. In that, case the flame is still burning when the valve opens and yields a high EGT. Even in engines running under load, it is known in a test cell that the flame may not completely burn until 18" down the exhaust pipe.
BTW - we LOOK for trouble in the first few hours and can see ordinary things that seem out of expectations. It may be nothing. Let us know what you find.