Air issues from injector return pipe

Hi all
I am have lots of trouble with my 300tdi, it keeps loseing power like fuel starvation whilst on a run, I have replaced the lift pump and run clear pipe from it to the fuel filter ( this appears air free on the drive when revved). I removed the injector pump return pipe and ran it temp into a jar, started the disco and there is lots of air and it filled the coffee jar in under a min, is this right.

Cheers

Rob

Fill rate sounds about right but air is wrong-check your injector leak off pipes for leaks-also try clear pipe from fuel filter to injection pump to make sure what is going in is air free,you need to find the source of air and eliminate it.