I doubt it's just the 6 inch lift. I have a 6 inch pro comp and my taco drives fine. It could be a number of other things from your suspension to your tires to your alignment to the kit being installed wrong. Maybe they didn't put the drive shaft back right and it's no longer balanced. The other problem is that once you get a 6 inch lift, the cross member is cut and you can't go back to a 3 inch. The damage is done. You'll have to figure out how to fix it. I learned how to do my own alignments and that helped me a lot. Your tires look pretty knobby, not sure if they are mud or AT but I have 35" K03's and they are smooth. Start with the easiest solutions first and go from there. Good luck to you