[scottfab]

Just based on your description I'd start with
a common issue. It's the little hose running up to the
MAP sensor (at the read of the plenum). I can fill with oil.
That gurgling sound you describe sure sounds familiar to that.
If after clearing that next I'd check for any codes set.
Even if the SES (service engine soon) light is not on you may
get a leg up on things by looking there. Some codes if transient
don't set the SES light.
I assume you have a manual? If not we can help you along but
they are really invaluable.

If the stumbling kicks in when the ECM goes to "closed loop"
(warmed up) then there is more to do to isolate but let's see how the MAP hose check turns out.
Some things to tell us are:
1. Does it accelerate ok at WOT?
2. What's the fuel pressure?
3. Good solid spark on each cylinder when you pull each plug wire
out a few inches?
4. How do you feel about pulling the plenum if needed?