Just recieved my srt8 and noticed that the valve caps on the tires are green and have N2 on them. I asked the dealer and he told me he doubts they put nitrogen at the factory in the tires but they can put it in at the dealer for a fee. So do my tires already contain nitrogen and who put it in there. If theres no nitrogen in my tires, why the special caps ? I asked my dealer to double check and he hasnt gotten back to me yet. Thanks.