Ima gonna lose it! cyl 4 misfire

[TB66]

I have a 97 PU/4 cyl. I hope someone can help, if they have encountered simular situation......I had a #4 cylinder misfire diagnosed when engine light tripped. It only trips when I am going up hill and then on the way down when I let off accelerator it trips. I have replaced A/T sensor, O2 sensor, rotor, cap, plugs, wires and just recently mechanic told me it was the EGR sensor. I replaced the EGR. On my way home, (FRI nt.) it trips again, usually at about 55-65, when I back off the accelerator. I do actually feel a slight shudder accelerating and deacceleration between 50-55.
My gas mileage has gone down 100 miles on a tank of gas. I have also tried fuel injector cleaner, and air filter. I just can't afford to keep replacing these sensors in this hit and miss game. Does anyone have any ideas? I have read other threads about this but none reflect my symptoms. Thanks for any input..

[JoeyS]

I had to replace the crank position sensor on my 98 4cyl a few years ago...
It was giving me a cylinder 4 misfire as well. Haven't had the problem since.

[jonx4x4]

Have you had your compression checked? As much as I hate to think of it, it may be a busted ring...