suspension? What is lowest I can go with torsion bar suspension without compromising the suspension.

Using the torsion bars for lowering is really just removing tension from the bars, letting the truck sag under it's own weight. It will ride a little different, and you may have to adjust the camber on your front wheels. Just make sure you don't put the cv shafts in a bind if it is an awd.

dont lower a 4wd put a 4-6" lift and 33's under it

Being that its an AWD vehicle, Any amount of lowering will compromise the suspension.