gordon, the castor rods do influence the car's driving straight or pulling left/right. I had the same problem with the black GTS (pulling left) and with the GTR (poor front camber).
for the GTS, i got urethane bushes from UAS to replace the stock ones (leaking) and then went for a wheel alignment. The car was driving straight after.
As for the GTR, i got the whiteline camber bush kit for the fronts. I think it allows setting for +/- 1 degree than the stock ones. New tyres went 2 weeks ago and i set the front camber at -1.25. Apparently from most advice i heard, the best camber settings for front is -1.5 and rear at -1.0.
another thing to remember though is that if you mess around with the castor, your camber will change and vice versa.
smell the chicken yet?