Mooney time

Experienced the same problem in my O. We replaced the vacuum line going from the shuttle valve to the stand by pump. Instruments weren't affected, but your right. It's a mess and you'll go thru a bunch of pumps.

We have to do some of your maneuvers every six months with the FFA since we use our ovation on a 135 certificate. I found most maneuvers work best on the ovation at 17" and 2300 rpm, full rich. This gives you 125 kts, making steep turns a snap, and the simpler, the better. One thing I've found during checkrides, you don't have to show off how fast the O is, just that you can master the maneuvers, and it's much easier at these speeds than anything faster.