Does it always pull to the same side, Ed? If so, you've got a couple things to check:

First, is the camber set the same on both sides of the truck? More negative camber (tops tilted in) on one wheel will pull towards that wheel.

Next, you're sure you've got the steering links on right? When I got my truck the PO had put the right link on top of the steering hub and the left one on the bottom, and the right wheel had some SERIOUS bump steer. He also had a "left" steering hub on both sides of the truck, compounding the problem.

Have you got the steering links the same length? The truck will pull to the side with the shorter link during acceleration (suspension rise).

You can also check to make sure that the cross-weight is even. If you've got the left front and right rear wheels pushing down further than the right front and left rear, the truck can still sit level but the left front will have more grip, and will probably turn away from that side. If you've got a shock stud on the wrong hole, you could get this happening.

Is it possible that you've got more flex in one suspension arm than the other? I experimented with custom aluminium rear arms for my Volcano and I didn't have a 3mm drill so I used 1/8" (3.175mm) and there's a bunch of slop that toes the wheels in on acceleration. It turns one direction on acceleration but tracks straight at speed.

Finally, I had bad problems with the original tires balooning - they'd all baloon at different speeds, so at first it would go left, then right, then straight.