Not too long ago I had an E90in the shop that had very low compression on #6, after a leak down test, I determined that one of the intake valves was leaking. I pulled the intake manifold and found the DISA valve pivot pin came dislodged from the DISA unit and was pinched between the valve and the valve seat. That was the very 1st time I've ever seen that (not common at all, but worth looking into). You can remove your DISA valve to check that it is intact. If it's broken, remove the intake manifold and look at cyl #1 intake runners/valves for an obstruction. The pivot pin is plastic and did not bend the valve in the situation i described. Hopefully you will be this lucky.
If you do find something stuck on one of the cyl #1 intake valves, turn the motor over by hand until the valves are open and try to remove the obstruction, being careful not let it fall into the cylinder.
Last edited by fastjasonbmw; 08-23-2012 at 10:36 PM.