I have a holley on my supercharged engine. I've externally referenced the powervalve, as you do. She's been parked up for a few months, and I took it out today, and went over to my workshop to do the exhaust. It seemed to run poorly at cruise throttle, and didn't want to idle. But would sweeten up (Somewhat) when accelerating. (On boost)
I pulled into the drive, and it was running like a bag of @#$%. I pulled the spark plugs to see how they looked. The first two were textbook perfect. The second two were as black as your hat. (It's an inline four) I couldn't see how two plugs could be black, and two not. Then I twigged that the vacuum feed to the powervalve comes from the runner to the rear two cylinders. I pulled the hose off, and found that there was gas in it. I plugged the hose at both ends, and it started running right.
It's no big deal to stick in a new powervalve, but I'm poor, and don't want it to happen again.
Whats the fix to prevent powervalve failure? I don't want to give it WOT without the enrichment of the powervalve, so I needs to be fixed. Also the valve that's in there is only a few months old.