2002 525d se auto tourer engine rattle

[grahamwalker295]

Hi All
I just had a replacement engine fitted(47k miles), my 140k one fell victim to the swirl flap problem that doesnt exist according to BMW.
When running at say 30mph and I put my foot down it goes great, really quiet too, and the mpg is superb, 42mpg at 70mph, measured over 50 miles.
Problem is when I am setting off, it makes a nasty rattle and will not pick up speed, unless I floor it. this especially on a hill, better on the flat.
I can press accelerator and nothing happens, not even fuel usage guage, but if I,m in neutral I can press pedal and it revs sweetly. I did think of pedal potentiometer at first.
I swapped the pressure controller and long vacuum hose, also replaced maf but secondhand one.
Any thoughts or suggestions please, this one has been de-flapped by the way.

[witeshark]

Mostly a guess, but how are the fuel filter and pumps, especially the high pressure pump?

[grahamwalker295]

Hi Whiteshark, thanks for the reply, I changed the Fuel filter 2 weeks ago, and the High pressure fuel pump was reconditioned.

[witeshark]

Have you had a read of engine computer codes?

[grahamwalker295]

Thanks, I have had a read by an indy, there were no error codes, there was earlier an error code relating to Boost Controller, the only thing I could find was a boost pressure controller. It has 2 vacuum pipes, replaced those too. The code was cleared after that.
Some people mention that the vanos unit could be to blame.
I also read that it could be the ecu, doesnt that advance and retard the timing, wouldnt that make it rattle, also I had it remapped in the early days, now with a replacement engine it could possibly need re-mapping, just dont want to fork out another £250