Originally Posted by schpenxel

To add more to the BMW mention earlier.. the valve coking was having a pretty large impact on those. BMW uses a system called valvetronic that varies how far the intake valves open. They literally use that as a throttle instead of a throttle body.. only BMW would do such a thing, but do it they do.

But I wonder if that makes the valve coking issue that much more obvious on them. I know they are known to run like absolute crap when they need the valves cleaned.