IF IT IS A PLUG IT WILL BE OBVIOUS. A powervalve will have a spring and a diaphram,and a number on it like 65 which means 6.5 inches of vac ume is the opening point.when it opens it will enrichen the mix 8-10 jet sizes. Put a vacume gauge on the car and put it in gear and let it idle. Use a PV rated just below the reading on the gauge,so it doesn't open at idle but will open as soon as the vacume drops when you wood it..Almost all will have a 65 in them stock. They make a PV tester but you can usually tell if they are blown by sucking on them...if it opens and closes when you gently suck on it from the side opposite the spring it should be good. You could also probably put some fuel in the float bowl and hold the metering block on with your hands and hold it up and see if any fuel runs out....it shouldn't run out of the pv.