I have an 82 GMC Sierra 2500 Camper Special. The rattling of the doors can be fixed by cutting off 3/4" of 1/2" pex pipe, splitting it with a box cutter or a saw, spreading it open so it fits on the striker post like a sleeve. This replaces the original part and makes the doors latch easily. No more slaming or rattling.
There are tons of sites discussing Q-jet issues associated with the secondaries. A good one is:
http://www.thecarburetorshop.com/Troubleshooting.htm