Idle drops/engine bogs in gear (auto)

[tsuave]

whenever my 90 celica gt goes from either Park/Neutral to either Reverse/Drive the engine bogs down and the idle sites less than 600rpm....it used to do that with a/c on but i changed out the AC VSV and now the AC barely affects the idle. what could cause the very low idle in gear....what should idle be in gear....i know in park/neutral it shoudl be 750-800. i even tried jacking my idle up to 950ish and it still drops to less than 600 in gear....is there a differnt idle adjustment that only affects in gear idle, is there another VSV i should check or whats up.......

any clues?

[Pineapple]

Once the engine fully warm up, it'll drop to around 600.

[tsuave]

but the car idles very rough when it goes below 600 the whole car shakes......and when you put a/c on it seems to make it slightly worse...