i have a 92 four door bronco with a 7.3 idi that has a acceleration knock and a studder or a miss at higher rpm and know billows out blueish smoke, but if u accelerated hard it cleans ups and blows a little black smoke but has a bad acceleration knock. I jst replaced injectors(brand new not reman.) glow plugs, return line kit. im thinking that the Injector pump is going? it start great when its cold or hot. the smoke clears up at highway speed but studder's.

 

I would put my money on air in the lines still bleed the **** out of it because these at mechanically driven engines you can't have any air in the line, it it was a powerstroke you wouldn't have a problem but i would try the air before spending 500 on another pump