I seems my IMRC is actually ok. Just from revving the engine with the car in park, I can see it open the secondaries fully in the 3,000 - 4,000 RPM range. I just completed a rebuild / thorough cleaning of the LIM, UIM, TB, etc. There was some pretty heavy carbon buildup inside the intake (at 73k miles). I used a Berryman's chemical dip to soak all the aluminum parts and then used some B-12 to finish them off. I gave the injectors a little squirt of B-12 to remove some of the gunk built up on them. I replaced all gaskets, o-rings, PCV valve and checked the operation of the IAC. I also cleaned the MAF with some electronic contact cleaner. I originally started tearing into this thing to fix a problem where there was no horsepower in the 3,000 and higher RPM range. The Ford dealer wanted to replace the IMRC and do a few other things for $1,400 - I decided to take care of it myself. ;-) After all this work, I got the power back! It feels very strong in the upper RPMs. I still have a little hesitation at the low end - not quite sure what that's all about yet.
Also, FYI - my car failed a recent inspection - I had a check engine light on, so I figured it probably would. It failed because of P0420: Catalyst System Efficiency Below Threshhold (Bank 1). It turned out to be faulty catalytic converters. The dealer replaced both of them free of charge. :-) They told me that emissions components are covered up to 80,000 miles. That was news to me, but I won't complain.
Thanks everyone for your input. I got a lot of useful info from this site and these forums.
