If you can see the "twist" with your eyes..check everything through again, measure and give the tricks mentioned another try. Get a helper to eyeball everything when you try to twist it straight. If it won't settle in straight by itself, though, using the tricks mentioned, and you have to force it, something is bent, or you didn't loosen everything you should have. Top nuts, (tap tubes loose from upper tree), bottom tree pinch bolts and center nut, fender stays and brackets, axle nut, axle pinch bolt...everything just a bit loose. Wiggle bars left and right and let them settle into a midpoint and pump it up and down from the riding position, and stay sitting on it, keep it upright and let somone else start to tighten the items, top to bottom. My bottom tree is not keyed, but mine is a MK1..Mk3 might be different. Don't forget to tighten ANY of the items you loosened, or we will be reading about you in the news.
If you can't see the problem, but just notice the problem when you drive, check isos, check top motor mount, check action of the sliders, oil content of the forks, swing arm, rear shocks, etc. Any number of things will cause a bike to not drive straight.