Vacuum Generator

The yellow "check engine" light has been coming on in my '93 F-150. I had the local dealer check it and they said the "vacuum generator" was malfunctioning or bad. I have never heard of such a part. Does anyone have any experience with a vacuum generator in an F-150? Where is it located and is it something that I can replace myself?

Also, I've been getting a bad "pinging" noise on acceloration. I'm suspecting that is has something to do with the vacuum problem -- something like the distributor not advancing properly.

Thanks for any input on this!