[ront]

1994 Buick LeSabre
3800 engine
148,000 miles

Engine misfires/chuggles at part throttle and light load (about 60 mph). Has good acceleration/performance otherwise.
P1406 History code.
Scan tool shows EGR Actual % swings wildly when the chuggle happens but the EGR Desired is steady..
Engine runs great when EGR is unplugged.
Tried a new EGR valve and it didn't fix the problem.
Intake manifold vacuum is high and steady when EGR is disconnected.
I could use some suggestions!!!!

Thanks