A warped rotor will cuase the pull, a stuck left caliper or the right side caliper not fully retracting will also cause it to pull. A normally worn idler arm will allow it to wander, but noit usually pull hard. Worn out lower A-arm bushings will also cause it to wander and clunk on take off and breaking, but not pull like you are experiencing.

I would start with the breaks, pull the wheels and see if the calipers are working properly, check the pads-they should be worn about the same, and spin the right rotor to see if it looks warped. If the breaks look good then look to the idler arm and the rest of the steering linkage.