I need some advice

[macascal]

hi there its max here

well I have a jetta 4 1.6 sr akl motor ive been having issues with it burning rich ...when I rev her up certain times I hear a pop sound from the front of the car like from the engine bay...its also very heavy on fuel ....I have done a full service, I have changed temperature sensor, I have changed oxygen sensor, I have changed plug leads and I checked vacuum leaks and all that is in check I have enough power on the freeway but sometimes taking of is a problem where it will hesitate and then move. Does anyone know what I should check next or what the problem may be....?
thanks