1997 Ford Taurus 97 Taurus SHO hesitation.

My car has been hesitating at idle for a while. At first it was very random. Now the hesitation is almost always there. In the last week the engine hesitated 5 or 6 times while slowly cruising, but for the most part it's only at idle. It almost feels like it's going to stall sometimes, but never does. The car always starts right up and within a minute or three the hesitation starts. The car runs great when moving and is in great shape aside from this minor issue. I've had the entire fuel /induction system professionally cleaned. I replaced the spark plugs, air filter, fuel filter, fuel cap, checked the egr, checked the pcv, and visually inspected most all hoses. The next thing I plan to do is check the intake manifold pressure. I also thought it might be a restricted passage or some kind of vacuum leak, but I'm not sure how to check these. If I could figure this thing out the car might have alot of life left. Do you have the answer?