Dave, believe me, its bollox Wankers

What its doing is telling the ecu that the engine is slightly cooler than it really is whick in turn ups the injector duration somewhat.

On 90% of modern cars this is usefull as they are mapped to run 1 or 2 lambda points on the lean side for emissions and economy. However, when your engine really IS very hot and the ecu needs to retard the timing to stop detonation, it wont as that resistor has put a delay in the system

Also,
Give her a try at starting and running cold without teh coolant sensor plugged in to enrich her for you

Wankers mate....