Engine no power when acceleration i ...sometimes engine is good after 3 days no power again,,

leaves catalytic converter expensive replacement

Try clearing the throttle body and IAC solenoid

Engine management warning light on ?????? What DTC'S - diagnostic trouble code's stored in the PCM - engine computer ? Should have DTC'S stored

Go back to that VW dealer and complain. I'm sure you payed plenty, and I know in my shop, if a customer's car is not repaired to their satisfaction, I want to know, and make it right. Sometimes parts can be bad right out of the box, and sometimes problems are misdiagnosed. Go back, but don't agree to pay for anything untill you get a satisfactory explanation. Good luck.

Is this a diesel?

sounds like your lifters or valves are rattling!

try a new one or try fuel filter

You have to clean up the fuel pump, and see whether it does or not require replacement. Do also the same with the starter engine, and see if the carbons are in good state or not.

Replace your fuel filters.