Jetta 5 2.LT FSI - Missfiring

[BLACKMAMBA]

 2006 model jetta dsg BWA motor - 163 000 KM
the car has been missfiring  for a while...

agents first advised that it was the coil packs, had that changed and the problem is still there.
Agents then advised that the injectors are a problem..R 10 000 to have them replaced 

we tried injector cleaner and stil does the same thing.
The car misses at low rpm and then at high rpm's its ok.

Any help will be appreciated

[Granta Gti]

Air mass meter?

[topher]

they should be able to identify which cylinder is misfiring, and swap the injectors around to test if the misfire moves with the suspect injector. if they're saying all cylinders are misfiring then its a little naive to assume all 4 injectors have developed the same fault. have they tried new spark plugs and addressed the most common issues of leaking diverter valve or pcv?

[BLACKMAMBA]

are there any tests we can do at home ?

agents are just assuming  and i am getting billed.