My 1997 TJ has a fairly severe stumble, especially when the engine is cold. It starts fine, idles fine and generally seems to work ok once fully warm.
If it was a carburated engine, I would say it required an accelerator pump.
The IAS motor seems to function fine. I just installed new plugs, wires, cap and rotor (just normal maintanance).
When I removed the old plugs, which have been in it for at least 3 years, they were too clean. As in, not any color to them at all, no carbon, as if it has been running extremely lean for a long time. The problem of the stumbling (or bog) has been slowly getting worse.
I dont think there is a vacuum leak, as the engine doesnt ever surge or wander. Vacuum at idle is 18" at 750 RPM.
My intitial suspician is either the fuel pump, or the fuel pump filter.
Hopefully someone in the group can give some insight into the problem.

Cheers!

Rick in Canada