I have been trying to fix my truck and just cant seem to figure it out, biggest problem is its my work truck so i really need it ASAP. ANY help would be GREAT !! Thanks in advance.

Truck is a 1989 Fseries Superduty (I believe its the 350 or 450) with the gas powered 7.5L v8 engine, 120k, 5 speed manual transmission with mason dump bed.

Heres the problem:
Truck starts right up no problem. Has a miss at idle, but its not too bad. Truck drives at first ok, but then after a few blocks, it starts to stumble, buck, bog down really bad to where you can't even drive it. (the best way i can think to describe it is if you can imagine driving a manual transmissin truck, stopping at a light, then going from 1st gear and jumping straight to 5th. You give it gas, but it doesnt want to move - if that makes sense) At this point i have to pull over.
Another thing I noticed is that when the bucking starts in, the check engine light will go on for a bit then off, then on ect. Also, the temp gauge never seems to go past the 1/4 mark.
Truck has an exhaust leak from the gasket by the 1st flange / manifold

Heres what I have done / checked so far.
- Truck at idle, vacuum put to EGR - truck wants to stall. seems ok right? I considered maybe this is not a good enough test, should I just change the EGR?
- Fuel pressure regulator - applied vacuum, holding no problem, Ok right?
- changed plugs, wires, cap, rotor.
- Truck has 2 gas tanks. Tried running both tanks to see maybe the fuel pump in one tank is no good - run the same on both tanks.
- put fuel additive and fresh gas.
- Cleaned throttle body out with cleaner and brush
- changed thermostat.

I noticed that there are 2 hoses that run together down from what I would imagine is some sort of smog emission pump on the pass side under hood. The hoses just end down along the exhaust by the floor board.

ANY HELP WOULD BE GREATLY APPRECIATED !!!

 

That Check Engine Light is trying to tell you something, do not ignore it. Check for codes, then proceed accordingly. That exhaust leak is probably triggering lean codes, meanwhile the PCM is trying to dump in more fuel which leads to driveability issues.

Before throwing parts at it, check those codes. Next question is how old are the plugs/wires/cap/rotor and filters? Never overlook the basics, it will bite you every time.

Not sure how applicable this is for a '89 Super Duty as far as test connector locations go, but the procedure still works:

Ford Fuel Injection » How To Run a Self-Test

 

Thanks for the help, I did think about the lean factor with the exhaust leak and since you too mentioned it, i plan to fix the leak asap and see if it helps. By the way, that link you sent me will propbubly be a huge help. Thanks