hi 

car is 1.8t 4x4 

when running the car has a very loud hum coming from the rear of the car all the time not just on start up. dont hear it when moving but when sitting at a junction or traffic lights it can be heard and its quite loud, is it failing?? and could this be causing the jerking when accelerating hard??

Could be.  Is your filter ok?

Quite possible. Have you let the car run out of fuel before?. Do you allow it to run on reds? If the pump had a chance to dry out it'll be worn as the fuel acts as a lube for the pump. Check the fuel filter for wear or holes or discolouring.

Most likely it'll be coilpacks or Mass Air Flow Sensor (if turbo'ed).

mine is that nosy too...I noticed that 2 years ago,and is running fine since.I allways replace the fuel filter once every 2 years

the fuel filter was replaced about 4000 miles ago with a genuine 1 and yes to be fair it does run down to the red from time to time (me bad i know)

i have changed the plugs and coil packs in the last 2000 miles or so with genuine plugs but beru coil packs. the jerking is really only when accelerating hard eg overtaking and really feels like something breaking down under load or a fuel delivery problem. if anyone can remember way back when cars had twin choke carbs its a bit like that, when cruising the car ran fine but when flooring it and the second choke came in thats when the coughing starts. i have no eml light showing it was recently put on vagcom by a Briskoda member but nothing was found.i have changed all the vacuum pipes and fitted t a catch can and am about to change the n75 and associated pipework hopefully that may help.if not the maf will be next.