I've seen quite a few C90s and 0-200s stripped and engines that have been run leaned at higher RPM are much cleaner inside, ie piston rings free in their grooves, less soft carbon and cleaner valves. Also the C90 doesn't seem to like 2300rpm, seems to be slightly rough in that rev band. The fact that the Jodel is cruising nose low at that speed means a more efficient regime, with the cranked section acting to reduce drag and providing not much lift.