the fuel pump is driven off the camshaft.
It is indeed true that earlier GTI's had the revision A camshaft which is soft, leading the lobe to wear , which in turn reduces the ability of the pump to supply fuel (ergo owners see fuel cuts as the first idea somethings wrong, usually when mapping/with hpfp). I doubt thats your issue though (but worth checking)
I am however shocked about the response from SC.
Even the slightest indication you have a rev A and are having issues then you need to get it checked. pump off, and check the cam follower / lobe for wear, not turn down the map!
buy a new follower and change it while the pump is off
![happy2 :happy2:](https://www.mk5golfgti.co.uk/forum/Smileys/newsmileys/happy2.gif)
VW may even warranty it if its worn. (if you put the std internal back in)
from what little I know the actuator is not something you go playing with without knowing what you are doing, I would only ever entrust this to a tfsi specialist (e.g JKM) who can log the car fully to ensure its set correctly. Its not something to my mind you just 'tweak'
![surprised :surprised:](https://www.mk5golfgti.co.uk/forum/Smileys/newsmileys/surprised.gif)
as others have intimated, Id suggest getting the car healthchecked (cam follower etc) , flash car back to stock,reset the handset and sell it, then move on to REVO/GIAC/APR
(for the K03 I'd suggest REVO imho)