My truck never sees anything but ACDelco or Chevy dealer parts, and I have never had any problem with them. They may cost more, but I know they are going to work. I made the mistake of trying a generic ignition module on my truck. I wound up with three bad modules right out of the box. I brought the last module back to the big name chain parts warehouse for a refund, and went to the Chevy dealer. The GM module costs half again as much as the one out of the parts dealer, but it worked. From what I understand, a lot of the electronic components sold at the parts warehouses are refurbished rather than new.
I made the mistake of getting a refurbished radiator once. The POS rusted through less than a year later, and all the warranty would give me was another refurb. The original parts store told me that it was new

. They saw the crew cut and military ID and automaticly assumed that I'd be long gone before I had any problems.