If you hear a whistleing sound when you press on the gas peddle ? But after i put belt conditioner spray on the timing belt it sounds clear. but after a period of time the sound comes back

You might need a new belt, or the spring in the belt tensioner is weak and not holding the belt tight to the pulleys, in which case that will need replacing.

Check this items
1 belt idler pulley bearing may be going out
2 belt tension pulley also bearing can be going out
3 accessory belt tension-er can be going out, this gadget keep a high tension on serpentine belt, if spring weaken can cause belt to be loose and slip around the pulley. replacing belt is also good idea if its has high miles on the car..spray any lubrication on any of those will be temporary fix but will come back. hope that help some..good luck!