It's possible that your left torsion bar is wearing out. It's also possible that your front left shock is be shot. As far as I understand, the torsion bars are springs primarily responsible for the height of your front end. If the bar is wearing out, it won't have as much spring in it to return your truck back to a neutral position.

You may want to try tightening it. It's a fairly simple thing to do. You just need two 19mm wrenches. If you decide to do this, here's a guide:

Tosion Bar Adjustment

Be careful, of course. You may need to bring your X in for an alignment after adjusting making the adjustment.