It has probably been discussed before, but i didnt have any luck searching for it. The 07-09 4.0 has 239 hp, and the 10-12 4.0 have 260 hp and keep the same fuel economy? I am wondering if anyone has narrowed the gains down to a kit or list of parts that would upgrade the previous years to the performance of the new ones.... I have read that the new engines have roller rockers, that is the only thing I know for certain that is a bolt on difference. Maybe there is a different exhaust too? Anyway, you see where i am going with this, any knowledge on this would be appreciated, thanks.