The TIT limit is often misunderstood -- it is not an instantaneous limit. It is a limit for continuous ops at max rotor speed at 1650dF, which would likely only occur at critical altitude. This seldom the case, so there is a buffer built in. You can safely exceed the limit for the time it takes to find peak and reset the mixture either ROP or LOP. Most POHs list this a five-minute period.
I can't say I understand how the limit is set in place but the PA31-350 leaning technique for LOP is quite specific to not exceed 1650F. It states if 1650F is reached prior to peak then reduce manifold pressure until a 75F drop in EGT then lean through peak if possible until 50-100F LOP, increase MP again not exceeding 1650F and lean mixture further to 1625F. Taking care to remain smooth operation all the while.
All the turbine aircraft I've flown it gets pretty serious if you exceed the maximum TIT limit at any stage of flight for any length of time.
I agree with most of the stuff regarding the LOP stuff but the 1650F in the Chieftain is listed as a red line limitation. The Seneca II also lists 1650F as a red line limitation, havn't got a III manual at hand to check that on the KB. Had to give the engine manual away with the aircraft so don't have access to it any more.
Don't mind the argument for LOP stuff but it will take a lot of convincing to take the needle through a limitation.