Hi im having similar problem with my s14 regarding the rev limiter hitting at 5k rpms i read about ur 5th sensor idea..is it located on the bottom of the transmission or the top side? and if im siting in neutral i can go all the way to 7.5k rpms but under a load im stuck hitting at 5k rpms...i have a ka24de engine and have replaced the maf map and even tried a friends ecu and still no luck, so much appreciate ur advise on the thread