1995 gmc 2500 egr vacuum valve activation
 

1995 Gmc sierra 2500 5.7lt. has egr vacuum activation at low rpm's. Does anyone have information of parameters of vacuum valve activation. Activation at low rpm's is causing drivability issues. Checked wiring and grounds ( all good ). Also have canister purge vacuum valve activation at same time as egr vacuum valve. Have hit a wall with this, any knowledge would be great.