OMEGA in Manchester UK makes very good and versatile range of high temperature thermocouples, U might want to pick a hand held Infrared Thermometer (iR2 SUPERMETER) or a Thermocouple with the probe elonagted by insulated thermocouple wire. Check them out on www.omega.co.uk.
What sort of Injectors are on the engine? The Hydraulically actuated and electronically controlled injector types are the most sensitive and thus if one of the twelve( i assume a 12 Cylinder Engine)is not firing at optimal capacity, it can lead to loss of compression in the particular chamber.
