I had to remove my pump and extend the slots slightly, before it then started to machine gun, backed it off a knatts tadger and it was much better, basically your timing chain has worn and is throwing everything out.
On the back of the pump is an inspection plate and under this is a timing mark, then using the flywheel timing mark you can set it up as per the book, 17 degrees btdc iirc problem is as the cam is also out it doesnt really help plus you then have to bleed it all up again and we all know how much fun that is.
So in a nutshell your motors getting tired
I cant recommend the tdi engine enough its transformed my car
Lynall