Loke Sølvåre

A couple of months back my audi startet getting harder to start. I blamed the extra cold winter and a poor battery. After a battery swap, which helped a little. I had a long drive where my car started "coughing". It would lose power, and I would get a 1-4 seconds lag when pushing the gas pedal where nothing would happen. After driving for a while I eventually reached my destination and parked. And after that it became impossible to start.
I have replaced the fuel filter.
Brought it to a mechanic who told me the problem was a faulty fuel injector, the one with a needle sensor. So I replaced that.
When I try to start the car, it cranks but never quite get started. Except when i air out the injectors and tow the car while trying to start I sometime get the car going. But it still coughs and jumps t and as soon as I park it it's dead again.
I recently also checked fuses that are connected to the fuel pump and injectors but now I don't know what else to try, please help!