2003 Buick Century EGR electrical

Egr checks out fine off car, except when I did the 9v test across solonoid leads the prindle only goes down 1/4 of what I can push it down manually if take top off valve. Hooked up I can push prindle down with screwdriver ang get 3.58 v. Before screwdriver bottoms out against body. Whole solonoid checks out OK. NOW, on car I get the.78v. Prindle position reading at iginitio on or car at idle. Drive car down road and the voltage changes only.02 volts back and forth. Take off manifold and watch prindle whilI rev engine and prindle does not move. Will move with 9v batttery though. Am I missing something or what. Car will run for awhile on highway and then w/o reason just go throttle dead and engine will idle roughly for about 40 seconds beforre it wants to respond to throttle again. Take off and run for 2-3 miles and then same thing. Engine use to code 101 but is coding nothing now. Replaced MASS, MAP, TPS, vacuum test-held, backprressure upsstream of cat. 1#. Car use to go to no throttle and sometimes die going up hills, but since replacing TPS, it does not.
Is the egr bad or is it just not getting signal from computer.
CAR WILL RUN FINE WITH EGR WIRING HARNESS REMAOVED. Made 200 mile round trip with it off. Also, car would run fin all day in city under 50mph for the 2 months I have been fighting this problem.