Loud engine noise

Hi I have a 2001 Jetta GL 2.0l gas 5 speed with 190k. It makes a loud whining sound when in 5th gear @ 3600 rpm's... Only at that range.. Not at 34,35,37, or 38 or after. It sounds like I needs another gear. I've replaced plugs-bosh platinum +4, ngk wires, new coil, air filter, fuel filter, cleaned MAF sensor, oil change and a lot of other things. Please let me know if I can do anything else. Thanks