I'm in the same boat.
All mods and vanilla feel like driving a boat in gp4 until I use the 2006 mod and everything feels perfect.
Why,the others are different,I don't know.
Been tampering with wheel rotations,axis sensitivity,gp sensitivity at low speed settings for 2 hours now going back and forth like a maniac and the G27 just doesn't feel right until I load up that 2006 mod.
Anyone got defintive settings for the G27 as I've searched this forum and come up empty?
Will search some other sites also for ideas.
P.S. There i surprisingly not much about this wheel with gp4 on the net.