I have noticed that I have lost a tremendous amount of power in my 530. Seems to really hesitate above 3500 RPM and lacks the acceleration that it traditionall had. My most recent replacements were a battery, coils and the crank position sensor. Once on a while it throws a catalytic converter code, but that only happens about once a month. When I first start it up, it idles fine. But pressing the gas all the way down, it stutters and gets stuck around 3500 RPM for about 10 seconds, exhaust smoke is a bit white and it smells like it is running very rich. Any ideas without taking it in to the shop? Could a burnt cat cause the robbing of power? Or is it more likely that could be engine seals? When I changed the coils and plugs, I did notice some oil pooling in the plug channel and some plugs were fairly saturated with oil.