Guys I have been researching this and have not been able to figure it out completely. I am guessing there is very little difference in performance between the 373 package and 355 stand alone option due to the tire height 18 vs 19 rims which would offset the gear ratio. The difference may come in with the better traction of the wider summer tires for the performance package. Now I have seen on the old 2014 track packages that redline of 7000 would allow you to go 114 in fourth gear. Would it be the same for the 15? I was really hoping to be able to get more than 114mph and maybe I should have went with the 3.55 stand alone option to get up 117 in the 1/4. although I may have a taller tire when I put the slicks on.