Leadfoot:
We were curious about a vacuum pump too. We just did a dyno test with my old school "D" motor 302 SBC. 3" stroke, 4" bore, AFR heads, tunnel ram w/ two 650's and a big cam, VP 110. We tuned the motor to 472.3 HP at 8,000 without our a vacuum pump. Put the belt on and made 492.1 at 8,000 RPM for an honest 20 HP. Aerospace Components 4 Vane pump 16.9 Ins vacuum which is high. We did not pull any oil into the pump and oil pressure stayed at a steady 90 PSI so it did not appear the pump was keeping the oil away from the wet sump pick up.
Horsepower had not fallen off up to 8,000. After 19 dyno pulls we decided to take the engine off the dyno, drop the pan and check everything before we moved up to the 8,400 pulls. It was still making about 3 HP per 100 RPM at 8,000 so in theory it could make a little over 500 at 8,400. We also had #7,#8 running a little rich so there may be a tiny bit more power in the carb tuning.
BR