Every time I had an engine that is pulling oil (minus putting it in the lifter valley), the way to stop it was to seal the engine up. Without air or blowby, oil can't be pulled into the vacuum pump. I had engines with huge vacuum leak that pulled 3 or 4 oz per dyno pull, at that point we stop and find the source of the leak.
Joe Agreed, I've also seen vacuum regulators fitted to valve covers 
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
| 
