As long as we are airing engine temp issues . . . I have one also.

I am running a TSIO550-EXP with one Lightspeed Plasma III and one mag.
For a year I would climb to cruise altitude, pull back to 32 inches and
2450 rpm, lean to 17.3 gph, and go merrily on my way.  EGTs were
1550-ish, TITs were 1580-1620, and CHT varied with the season (390 in
the summer and 350 in cooler times).  However about 4 months ago my EGTs
began to increase and with them the TITs.  Now to keep TIT below 1625 I
must lean back to 16.3 - 16.5 gph, and that yields a slower TAS.  

Anyone suggest a cause and cure?

Robert M. Simon
ES-P N301ES