i own a 2005 sti, the only mods i have on them on are: HKS carbon fiber cat back exhaust and blitz dual turbo timer. NOW when i rev my engine between 2500 and 6500 in gear or neutral, as soon as the needle hits 600 rpms the needle jumps up again to about 1200rpms. so every time i change gears this happens. i cant seem to find the problem. any input would help thanks.