I know I've seen posts about this, but;
a) I couldn't find them, and
b) I don't recall a solution

I've this problem a bit under 4.5, but after upgrading to 4.6 it was worse. Hot or cold, it would rev to ~2100 RPM's, then settle down after about a second to the correct cold or hot idle. I considered this a problem as the oil pressure showed zero until AFTER the idle was back down. Anyway, not what I considered "good" on a motor, regardless of temp. Anyway, talked to Randy at Zippers and he pointed out I could set the initial IAC home position lower in the "Basic Settings" portion of the software. It comes set at 100, so I lowered mine to 75, then 70. Perfect. Setting it at 75 still allowed it to rev a bit high when warm, but 70 allows it to startup with ~100-200 RPM's higher than target, then settle right down.

Just thought I would pass this along.

P.S. - This is NOT an issue with all Tmax's, so unless you've fiddled with it or see this problem, I wouldn't rush out and make this change.