I have a 89 f150 xlt lariat long bed 5.0 I purchased not a month ago, it had a miss in it and naturally I played on that fact to in turn get it cheaper.....well that has sh** in my face.... after alot of work it runs way better until load is applied, it idles and dies at idle and when it does actually idle on its own as soon as you put it in gear it will bog instantly and die and when it dies it makes a tapping noise after the motor is completely off... not the normal hot converter / hot oil noise either... also just noticed gas in the oil. Its a 4 speed manual if that matters. The CEL isnt on. And it has no vaccum leaks whatsoever... I hope I've posted this in the right place forgive me if I havent. I'm new to the neighborhood.

 

If you have a carbed engine, check the floats for correct specs....and what kind of carb?
Gas in the oil is not a good thing, as you well know...

 

Gas in the oil in that engine is hard to do, but the most probable cause would be a leaking fuel pressure regulator. There is a vacuum line attached to the regulator, and you can pull it to see if there's gas in there. If so, the regulator is leaking gas into the intake manifold, which can cause really bad running, and if the leak is bad enough, can find its way into the oil. Are you noticing gas smell coming out of the exhaust like it's running really rich?

Not sure about the tapping noise.

 

I'm normally in dents, I don't know much about newer engines, Gas in the oil us a bad deal. If you have a mechanical fuel pump, the diaphragm could be leaking gas into your crankcase while causing these problems. I would check the firing order and timing as well