We have to stop meeting like this ...
My experience in Oman (similar climes to West Africa).
Worked for an outfit that had Dornier 228 with Garrets, always problems in the summer (constant ambient of 45C+) Currently have a Twotter in UAE, similar climate again and the PT6, so far, has not given us any problems this past summer.
I have a South African contact with plenty of experience in this area if you are interested, drop me a line.