Nik, sounds like you have a powerful little K-80 for the density altitude there, and I would go with Dirk's suggestion to dial down the accel delay a bit and should mild down that transitional growling. Please let us know what your peak RPM EGT is. If everything is fine, I wouldn't worry about it, otherwise you may need the next sized up tail cone. By the way, the factory informed me that after their cleaning of the internal chemical extinguisher contamination, they rebalanced it and runs flawlessly.

Craig, thank you for your report from South Africa, make sure you say hello to Morne for me.

Cheers,
Barry