Did you get around to checking your timing?
The timing on the Express IS adjustable to a degree. But if it's too far off you need to replace your points.
Having your timing off can definatly cause simalier problems to what you're seeing.
As for the oil injector, what most people do is they leave the oil pump in place, and then connect a loop of oil filled tubing from the output to the intake. Gives the injector something to circulate. Then they just cap off the oil line nipple on the engine.
Also, what ratio are you running on right now?
And finally, pinging is usually a sign of pre-ignition.
I'm not surprised that ti only happens when the engine is hot.