Car = Golf GT TDi 150 (2003)

Newbie on here but this problem has been unsolved now for 3 weeks
I hope someone here can help??

Initially my car was taken to garage because it wouldn't start at all... RAC checked the car and confirmed that it was the petrol tank pump (a.k.a lift pump.)

When the car was at garage they removed the petrol tank and discovered contamination in the bottom of tank. It looked like a layer of Oil, which had been sitting there for a while and formed a lining on the bottom of tank.

Having cleaned the contamination out with a pressure washer and fitted a new pump the car seems to be running fine (drives a dream with no loss of power) and starts up first time when on the flat.

However when parked on even the slightest of incline it won't start at all?

The car has had 4 new injectors and injector loom fitted only a few weeks ago and having been under diagnostics several times everything seems to be running fine with no error codes.

When I try to fire the car up on a hill the car tries it's best to start but it seems like there must be a fuel fault somewhere???
Has anyone else experienced this or similar problem?

Any advice would be much appreciated.