yes sir , single turbo on the tsio520. the log manifold on the tsio520 is not the best @ LOP operations. I am aware of the 550's differences, i meant similar in the sense of the cylinders are essentially manufactured the same, similar overhaul times, and therefore maybe similar enough to compare to ? maybe not- they are twin turbo and the tsio550 tuned manifold does an amazing job allowing LOP operations, i believe your correct that LOP operations may be kinder since the 550's seem to "go further".
after asking around with some well respected engine shops more than a couple times now ive been told the TSIO520 is the kind of powerplant that requires a top or so to get to TBO. i was just curious how other operators handle top overhauls since the internet is full of "failure after top overhauls", and mike busch has published content basically saying you should never do a top overhaul.
i am thinking CMI has fixed their cylinder issues and a balanced pack from the factory would be the preferred cylinders.
thanks!