Im considering 4:10's on my 06. MOds: full exhaust, cai,tune and rear tire size 295's/35's/18's. Do i need to get it re tuned after putting in gears, if i dont how bad is my speedo gonna be off. i currently got a brenspeed tune do i need to get a new one from seth or can i manually do it on my xcal2 and still keep the 93 oct tune im currently running from him. currently running low 13's on street tires in the 1/4 mile, a change of gears gonna help me break 12's. and how bad would my gas miliage change. 80% of my driving is hwy.
Thanks, to anybody who can answer these questions.