I don't think it has much to do with Castor. I have pushed my castor all the way from 1.5Deg to 7.5deg and mine pulls the same way to the left.
It's a bugger on cornering to the right as it seems the steering is vague compared to turning to the left. At higher speeds it sometimes feels like it is going to catch me out, and with the amount of body roll I have on a 7.5" lift, it gets to feel dangerous sometimes, especially if it pushes you to, and nearly off, the edge of the road.
Lest weekend I was loaded with a fairly big sound system for a Gig we did, and I found it felt slightly worse with all that weight so high up.
David - Bfreesani
1997 Nissan Sani MK3 2.7TD - Hillbilly (SAFANI)
MQ Patrol C200 SFA
MQ Patrol H260 LSD Rear
MQ Patrol Transfer as second low range
33"x12.5x15" tires on 8.5J rims
DIY rock sliders