98 Kia Sportage can not rev over 2.5 rpm

hi,
need help, i had change my fuel injector,knock sensor,o2 sensor,mass sensor,timing belt. plus services all oils. but the problem still there. my KIA Sportage 98 auto 4wd, the gear sometime can ship to high but sometime remaining gear 3 or 4. when running at high way, the rmp cannot over 2.5, if over then that the car feel vibrate, then I have to let go the fuel allow the rmp drop to 2.0 . over all my KIA just cannot speed over 100 kmp. please advice where goes wrong? I had change so many part but problem still there. when use device to scan the car but no defect light turn up! or my workshop foreman is not good enough.