Review on Efficiently Functional: Delphi EG10099 EGR Valve for Optimal Performance by Craig Rossman

Bought the part with "scratches and dents" discount here. No scratches, no dents, but apparently the membrane was faulty. I didn't know before how to check if that holds a vacuum by pressing the vacuum port with your finger after squeezing the membrane. I originally diagnosed this part as a problem on my truck, but the problems continued. After rebuilding the TBI, replacing the EGR vacuum solenoid and replacing the spark plugs, I went back to test this part and decided it was bad.