Thats awesome, i wonder what i'd get with the b16 tranny for mpg. 35mpg though is sweet! Yeah its a six speed but very close ratio. I was in it today and at 80 we are at est.3700 rpm. The thing screams though. and for 46k miles in one year, the thing is a champ.GSR, USDM ITR, and B16A trans all have the same final drive I believe. It's the 5th gear ration that differs and makes the GSR a little more efficient for highway driving. Well actually I believe every gear but 1st and reverse differ but thats a different story. You'll be a bit quicker with the tighter gearing of the b16/ITR trans but for a DD unless it comes with LSD I would just pick up a GSR tranny. My GSR is moderately build and all highway cruising between 70-75mph I got that 35mpg. Course our cars are lighter than your buddies too. Isn't the SI a 6 speed and it still puts him that high in the rev range? Damn lol