cbr is dead on i have an auto with 3.73's and i have pacestter headers with the texas speeds x pipe and i need ear plugs when on the highway, and i have troble talking on the cell so..... if its an auto go 3.73 and also my rpms are pretty high but i go 70+ on the highway....its a big difference with a m6. but i get 20+mpg with 3.73's so im happy all around.