Hi Colin,
        I had a similar problem to you, my symptoms were :

        loss of power
        stalling
        hard starting after it stalled
        surging

I started to replace some parts, in fact I replaced ALOT of parts such as,
the ECU,fuel pump, fuel filter, AFM, idle stabilizer and it still didn't
work correctly. So I took it to my local mechanic who replaced the O2
sensor and the blue temp sensor it ran fine , for awhile. A week later it
started the same thing again. Took it back to the shop and they couldn't
figure it out. Finally had to take it to the dealer where they found out
that I had some broken wiring. It seems that the wiring from the O2 sensor
and the blue temp sensor broke and had to be replaced, they run to the ECU.
It was causing the ECU to dump fuel into the engine and run rich , hence
the loss of power, it just flooded it.  It's been almost 2 weeks and so far
and it's running fine now though yesterday it hesitated a bit. Hopefully it
was just the carbon build up and a couple cans of fuel injection cleaner
will clear it up. At least I have a warranty on the work performed at the
dealership. 6 months on diagnostic and 12 months on parts and labor.
        So check the wiring and I hope this helps.

Steven Min

95 Golf III
86 Vanagon GL
81 Scirocco S