Hi there
I wouldn't worry much about the potentiometer - it doesn't do as much as the pressure reg and is not adjustable as it moves with the flap (assuming the flap moves freely).

Are you saying it also has problems starting when warm? Even with the pedal slightly depressed?
The pressure reg won't do much on a warm start.
Have you checked there are absolutely no air leaks in the intake and all hoses (e.g. the vacuum hose to the ecu etc) are connected nicely?

the temp sensor when cold is appx 3300 ohm [range 1300-3600] when cold and 380 warm [range 250-390]. it's a good idea to make sure this and the wiring to/from it are ok (as you are doing).

if you suspect the fuel pressure is not held after switch off you could connect a pressure gauge to the cold start feed - min 2 bar after 20 mins engine off. Never done this, but I guess you could actuate the cold start injector when warm [into a container] and do the same again when cold in case there are obvious differences in pressure/delivery of the whole system (- the cold start inj isn't important, I ran mine always disconnected for UK weather).

good luck!