There's a TSB for pulling. Not sure of the cause. Several others for rattling:
Service Bulletin 165331 for Toyota STEERING | AutoMD
2006 Toyota Tacoma Steering Service Bulletin 165331
"Repair manual supplement: vehicle pulling to one side. Toyota all model years. *mj 2002 - 2007 model years. Toyota/scion models."
Besides the rack (more dangerous), it could be anything in the suspension.