Anbody have any suggestions. Ive got a 91 ranger w/ 4.0liter. Idles fine and seems to do ok if you a light on the throttle. If you get on the throttle it feels like you a losing a cylinder. ive replaced plugs, coil, checked maf sensor (data within spec). Wire were replaced not to long ago. could i still possibly have a bad wire.

 

I have had the same thing. I just got done cleaning the throttle body, MAF, intake tube, and the IAC. It's gone as far as I can tell, definately runs a lot smoother. I'll get to drive a little bit more tomorrow to see if it is completly gone.

 

I had this on a Dodge V8.
Moisture had gotten in the fuel system and over time had caused rust particles to build up and plug an injector. It would pass enough fuel at idle and light throttle but hard throttle it would drop a cylinder.
I fixed it by removing the injectors and using carb cleaner with the extension tube ,blow the crap out of the input side of the injector.

edit to add
Change the fuel filter if you haven't already