i bought a 2001 v6 5speed. the previous owner said he installed 373 gears, positrac syncro unit. my speedometer is off about 12-15 mph. going by gps i run 65mph, speedo says 80, rpms at about 2300 - 2400, tires are a 195/60/15. is there any way to sync the speedometer and maybe lower the rpms to runner better hwy. would taller tires be better. also have dual exhaust cross pipe, magnaflow mufflers, no cats.
thanks in advance