Mine does it too, it is like the engine drags when you are'nt on the gas. Doesn't happen if you keep the foot lightly on the accelerator tho... I'm beginning to think I need to try the fuel pump thing, since this has come up before for me, and others, and I haven't checked into that issue.
Just to clarify what mine does (if your's does the same thing) I'll be driving along at 60 mph and let my foot off the accelerator, and coast for a while, the engine coasts at the same rpm as I was driving at for a few seconds, then it seems like the bottom drops out from under her, and she almost downshifts (not sure) and the revs drop like 150 (or MORE) rpms( down to like 1500 rpm's) and drag the car down in speed for a few seconds, then after that few secconds, the rpms's increase back to normal (like 2000) and the car doesn't feel like it's being draged by the motor any more. Is this what you are reffering to? Mine does it and it peaves me to no end, but the solution I have found is to never let up of the pedal completley, just to maintain that matching rpm to the trans. It is a total pita, but until I figure it out, what can I do? I feel your pain tho... I've got issues too.