Well, I've just bought a 1k pot and the following resistors: 1.2k, 1.1k, 1k, 820, 430, 300, 200 and a few 110's.
Couldn't get the 1.5k pot so I'm initially going to try the 1k pot in series with the 430 resistor and slowly wind the resistance down and see what happens. I'm hoping to find the best compromise of performance increase versus smoke, CEL and glow plug light illumination. Once I have worked out the correct resistance, I'm hoping I can remove the pot and wire up the required resistors as required.
Watch this space................