It shouldn't push air out on the exhaust stroke or suck air in the spark plug hole on the intake stroke. The exhaust and intake valves should open. If you let air out on the compression stroke it will suck air on the power stroke when both valves are closed. Do you have a compression tester? Maybe you need a friend who knows what he's doing. But if you find one he'll probably want to switch it back to HEI and fix your original problem.
AL