When the vac. line is that is connected to the egr valve and the egr solenoid is connected like it normally is the car wants to die everytime i push the gas and let it go, but when it is disconnected from the solenoid, the car runs fine what should i replace, Its a 91 z28 305 TPI. When the defrost or ac is on ONLY when in park the car idle goes up and down what do i need to look at on this problem. Thanks in advance