really bad rough idle
 

I have a 87 chevy silverado 10 pickup 4wd with the throttle body injected 350. the problem that i have is that whenever i start the truck it idles fine but then whenever i put it in gear the idle turns really rough and shakes the truck. i have tried to fix this by adjusting the idle a little higher and i also put in a new IAC thinking that it was stuck but it ended up not working. someone had told me that around this year they had troubles with throttle body gaskets leaking? is this true. and if you guys can think of anything else that can be causing this it would greatly help. this is a OBD1 system so it only has one o2 sensor and there is no check engine light or anything in the dash lit up.

bump bumpity bump

The silence is probably because there's not enough to go on. You don't say what you've done so far but an air leak should affect the idle quality with or without the load. I'd start with which cylinder isn't contributing enough to the crankshaft output. Disconnect the wires from the spark plugs one at a time (they have a special insulated tool for this) and see which one has little effect on the idle quality?