Sorry in advance if there have been posts on this. I am needing to remove air compressor for the 8.3 in my 1990 M925a2. I read on a heavy equipment forum that the compressor needs to be timed to the engine. However, the TM's seem very non chalant - remove bolts, replace gasket reinstall compressor etc. Can anyone chime in? This truck is my first ownership experience in the Big world.