I have a golf 1.8 gti non-turbo. Symptoms include severe lack of power and rev restriction. Cat and exhaust are clear. Fuel pressure and flow are within spec. Throttle sensor scoped OK. Power and earth supplies to throttle unit OK. Disconnection of MAF has no effect. Originally code P1508 (Idle learned value) appeared. Replaced throttle unit with BBA recon, carried out basic settings, code no longer appears but fault still exists. I am using modis, anyone had this problem before. Any ideas welcomed.