Originally Posted by
t.er
I remember reading something years ago, where GAS did testing of the rear main seal, and simulated the O2 Pilot mod by applying the same vacuum pressure to behind the seal. He ran a smoke machine in front of the seal, and the smoke got sucked in. I forget where I saw it but I also remember seeing pics of the M54 rear main seal, most conventional seals have a coil spring around the circumference to maintain compression on the crank, but the M54's seal is low-tension and doesn't have one.
IMO the right way to go about this is either the GAS CCV, or the M56 valve cover - I wouldn't want to risk dirtier oil or blown seals with more crankcase vacuum