Around the 28 minute mark, they cover code 21
I've got a few GM Books on E4ME Quadrajet and Computer Command Control
Needed it when getting to the bottom of the issues with my dads '83 Grand Prix
I can scan some stuff up if you give me your Carbs part #
That Classic G Body video is really all you'd need to know
There's several reputable Quadrajet specialist rebuilders, one did a very nice job on mine
What's the Year/Make/Model/Engine Code?