So you removed the corrugated tube and the UIM to make sure there is no blockage up to the LIM and through the "stove pipe"? Also check the tube that comes from the exhaust to the EGR. These get jammed up with carbon and they don't have to be completely clogged to cause problems.

As far as the MAP sensor goes, you can scan and watch the MAP signal when the PCM commands EGR. You should see a nice deflection with RPM held steady.