I have a friend who has an L1 C28 and he has always had to light off at 8%. The outfit I work for has two of them and I have never had a problem at 15%. Go figure.
But we had one that, under high power settings, would droop to 94%NR and not recover. Changed everything they could think of(fuel control, governor, injector, rigging) and it still did it. It has been undergoing some paint and a bunch of other improvements so i wait to see if it still behaves the same way. Any ideas?