You need to make a new timing mark on you impeller fan, and correctly set the timing. I think there's an article on Pelican's page that will show you how to re-mark.
Air cooled engines are more sensitive to ignition timing. The biggest concern would be too much advance, which can make it run hot, and/or damage the engine. It's not easy to hear our flat fours ping, if the ignition is too far advanced. I don't trust timing a 914 engine by ear, just my .02
Your oil pressure light could be coming on because the timing isn't set right and the engine is idling too low.
Worst case scenario is your main bearings are shot and it's rebuild time, but unless you've got over 125k miles on the bottom end, that is probably not the case.
PK