I just purchased a 1999 grand prix SE with a 3.1L engine. the engine runs great however i was working under the hood and noticed the vaccum line running from the pcv valve to the intake then to a box( i think its the evap purge valve ) under the ignition coil was unplugged at the box . i plugged it back in and the engine died. leaving it plugged in and restarting the engine it would idle real rough and die if i didnt give it some gas for a min. unplugging the vacumm line again from the map sensor allwos the car to start and run fine. i am getting trouble code p0401 egr flow insufficient.