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

really hard without doing some sort of diagnostics. can be so many things.
compression
airflow meter
fuel pressure
cam timing
cam timing pickup
leaking / bad injectors
etc etc etc.

Did you find your problem cause I'm having the same problem

Book it in for a diagnostic at a mechanic.