As Steven has already said - if you get an X55/X56, first thing to do is open up the throttle and remove most of the "Grease" from the mechanism. That will make it 1000% better - the stiffness adjustment on the left will then work correctly instead of going between "Geoff Capes" and "Incredible Hulk" settings.
Never had a problem with throttle resistance on my X55, it is screwed down though.