A completely destroyed valve will leak fuel. The power valve comes into action when the vacuum goes low. There's no vacuum on a engine that's off, or on the bench. So the "didnt leak overnight" is inconclusive at best and completely out in left field - tells you or proves nothing other than its not obviously destroyed the same as a visual inspection would. A screwed up PV will open too early. The wrong PV not coinciding with idle vacuum will open too early. A PV that opens too early will make you run rich to varying degrees on everything below WOT.