Jonnyp11

I have a 96 c1500 extended cab, had the vortec 5700 put in when I got it after the original (smaller) engine and trans went out from not being maintained. Unfortunately my grandad had all the work done and trying to be cheap is costing him a lot, the wiring is hell, issues popping up left and right, he heard ~40k miles were on this engine but we think he didn't hear a 1 in front of that (might have 140k miles). The truck's body itself is going on almost 317k miles, and the paint and interior show that (surprisingly no rips and still good padding on the seats, no clue how cuz it hasn't been redone).

Now to the problem. I've been trying to see how high I can get the MPGs, and a turn I take off the highway every day (probably 30-40 degrees, not sharp at all) is immediately followed by a hill, so I decided to hold all the speed I could instead of accelerating to 50 up the hill. Went fine the first 3 days I think, but last Friday that ended. I don't remember any pop or other noise, but once the turn was done (~40mph) I could hear my exhaust sounded different, the engine was missing, I lost a ton of power, and it was backfiring pretty bad (especially while accelerating). So as far as I can tell, something came apart in the turn (remember it was put in poorly). I have looked at the engine and I haven't seen anything that looks wrong (outside the usual).

I just need ideas, I need the truck to work so I can get to school. Avoiding driving it for now to be safe but after tomorrow I'll have to drive it most likely.

Just drove again (short trip) to see if there was anything I was forgetting. I was going very easy on the gas, but it had not power at all, I remember on the highway I couldn't accelerate past 60 much unless I floored it and the toms would jump from 2 to 3k and climb fast. It feels like a 2L 4-cylinder is trying to move this thing right now. And if it wasn't obvious from the other symptoms, it's running rough, shakes a good but idling and revs up and down a lot