2000 pathfinder while driving sometimes it will jerk until I pressed the gas little harder, it is worst when air is on. While idling engine is smooth when turn air on it start to jerk .

I've been driving this car with no problems excellent until one day all of the sudden it just stop (engine dead). I've check sparks fuel is good, when spray starting fluid in the intake still wont start. I'm pretty sure it is the distributor.

I gave it to a friend that has a shop, told him what I thought it was, but did not want tell him how to do the job. He change the timing belt the water pump still won's start. After 4 months he put in a distributor and it started, but he said it was back firing and said that he found that the intake manifold was cracked.
He put in another manifold that I got from the junkyard and he said everything is good.
I took the car home right away it was jerking on the freeway, and when I use the air it got worst and also has a strong burning smell. It turns out that he did not tighten the head cover, oil was leaking.
I brought it back to him he then said it was a faulty distributor, he changed it and said my injector 4 and 6 was gunk up from cheap gas.
After 5 months and he want to charge me almost a grand, during this time I lost my job due to no car, I got mad and took the car home. He said he replace lot's of parts in there but wont give me a list of what was replaced.
I replaced the fuel filter, spark plugs, wire set. It still won't help.
Hopefully one of you geniuses or expert can help me

Thanks