The best thing to do is get a loaner car and leave the titan with the dealer until they can duplicate the concern. Nissan does not allow techs to throw parts at a vehicle in hopes its fixes said concern because the customer said something is wrong. The dealer has to duplicate the concern if no recalls or service bulletins are present. If its an issue covered under warranty Nissan should pay for a rental. I would ask the dealer to contact TECH-LINE to see if they have seen any similar issues to help the tech get going in the right direction.