My 85 190E developed a serious problem.

It started with some minor hesitation which occured a few times while I was driving, I knew something is wrong, now the car sounds like it's running on 2 cylinders.

I thought it might have been a spark plug wire cause one was damaged, I fixed it up but nothinging.

When I start it, it takes a lot more cranking then usual but it does turn over and start running, and it runs fine for a bit, then after a few seconds it starts staggerign as if something is holding it, the entire car shakes like crazy and I can hear the exhaust pulsing. The economy gauge goes 1/2 way up and when I try accelerating, the engine does not move until throttle is at 50%.

I need some help figuring out what this could be, any ideas please send them my way, I'm not sure what to expect, but my rotor cap, distributor arm wires, and plugs are all less then two months old.
it does not look like an electronic control to me, but I have no idea what it is so I could be wrong.

TIA

xp