Mitsiman - perhaps you can assist with this. Using the RPW full length header for the 4G94, where would the best place to mount the thermocouple for an Exhaust Gas Temperature gauge? Some of the gauges I have looked at dictate that the TC be mounted where the individual runners meet, but considering the design of RPW's header that places the sensor quite far from the cylinder head, and would not give an accurate reading of the EGT due to losses off of the surface of the header runners.

Also, has anyone tuned their motor using the EGT? Is this a good or bad way to determine if the motor is rich/lean? What is the optimal range of EGT for this motor when it is running properly?

 

Bad idea to use an EGT for tuning. (It's better as a warning indicator) Best solution is a wideband O2 with an accurate display (not just plain LED tree) , second best would be something like the GReddy AFR gauge which comes with its own sensor.