confusing engine problems

I have a '95 Xj with the 4.0HO and the 5spd manual. Lately the engine has taken to sudden losses of power, not enough to change speed much, but enough to be felt throughout the cabin. I understand all the theories behind the engine, though I haven't ever gone that far into one, but I'd almost think that a cylinder isn't firing periodically or misfiring nder pressure...I'm very confused about the whole thing. Any help anyone can give or just passing idea would be greatly appreciated.

first thing that comes to mind would be a clogged/faulty cat. convertor.

A cylinder misfiring, or an injector not firing, would likely be felt as more than just a loss of power. You'd feel it stumble or run roughly. I'm inclined to go with 89XJ's thought of a clogged cat, but also consider a clogged fuel filter.

If the power loss is felt as some kind of roughness, you should look also at injectors, ignition wiring, plugs, etc. A good place to start would be to hook up a vacuum gauge and see what shows on that.