1999 ford windstar pulls when I let off gas

1999 Ford Windstar When driving my 1999 ford windstar it pulls when I let off gas. When I hold the steering wheel in one spot and let off the gas the van wants to drift to the right as soon as I give it gas it stops and drives normal. Does anybody have any Ideas whats wrong?

While you left off gas, try to apply very lightly the brake pedal to see if it seem to cure the situation or if this make the van stop pulling on one side. If so I would suspect the right side caliper to stick which can cause the van to pull on this side.