It is not clear why you want the chip, so it is a bit hard to suggest something. Are you modifying your current motor or are you putting in a different one. Just putting in a different one would not generally require a chip upgrade, even going from 3.9 to 4.6.leadfoot said:I am getting ready to do engine up grades. I really want to use the tornado chip offered through this site. In my research I eventually came across the info that USspec ECU cannot be modified and that I would have to buy a euro spec ECU to rechip my RR, reguardless whether it was plug in type or not. I was wondering if anyone in the US has rechipped their ECU and if this was the case for them. I really dont want to buy things and return them back and forth over and over so any real experiences would be great.