Check the firing order on your spark plugs or that they are plugged into the proper slot in the coil pack. A crossed plug will feel like it's missing a cylinder ... which it is.
I don't remember when coil packs came to the Ranger, but it is easy to get the plug wires out of order 1-3-4-2. If you get the ignition timing off, it may have no bottom end, and only 'come to life' above 3000 rpm. Checking the belt for cam timing after putting it back together only takes a bit of time, so if you have any doubt, check the triangle on the cam sprocket being at the pointer behind the plastic button in the belt cover at TDC.
tom