1996 Chevrolet Silverado 96 Chevy z71. Surging, loosing power

The knocking seems to be coming from the top of the motor it only does it till it warms up and after it warms up is when it starts the surging and loosing power. Some of my friends told me my motor may be going bad but im not sure.

I did everything in the link you sent me this morning. Went and drove it about 10miles or so and it did fine and then it started surging and cutting out again. It acts up for a lttle while then it evens out and runs fine for a few mins then it starts doin it again. I have been to every mechanic in my town since it started messing up and they all told me it was diffrent problem I tryed everthing they have suggested and have still not figured out the problem.

And yes you are correct the motor in my truck is a 5.7L Vortec 350

I checked the fuel pressure and it was fine. Scaned for codes and it keeps popping up a random misfire. It popped the code up before and thats when I changed plugs and wires and had the timing set. The code went away for a few days then popped back up and has been like that since

I took it to a pro when the mifire code popped up and he said the timing was off so he timed it. Like I said I drove it for a few days after with no problem then it came back. Ive been to every mechanic in my town and have done everything they said. I went to a mechanic in the next town over from me and he said it was not misfiring and that it seemed like nothing was wrong to him. Yet the misfire code is still up and its still surging! Im lost I dont know what to do. Im about to the point of dropping another motor in or just parkin it in the backyard and let it sit.