Caterpillar C10, C12 fuel injector replacement.

I was walking by one of my co-workers today who was replacing a fuel injector on a Caterpillar C10 engine.  And he told me the coolest thing.  He replaced one injector on the diesel engine and it was the #1 one injector at the front of the engine.
   I asked him how did he know that injector was the problem,  now traditionally when you have  a problem with an injector you will hook up the computer and do a cylinder cut out test.  This test will shut off each injector one at a time.  Each time it shuts off an injector you should hear  the engine vibrate excessively and generally run very rough.   When it cuts out an injector and there is no change in the engine rpm/ vibration; then you have isolated the problem injector.
   In this instance we did not have a computer that could perform a cylinder cut out test.  So my friend decided to run the engine for about thirty seconds and then go to the exhaust manifold and feel it with his hands.   The cold part of the exhaust manifold will reveal which injector is not firing.  I thought that this was a pretty ingenious way of troubleshooting and very creative.  He found that injector #1 was not firing properly and so he replaced it.
   Now the thing you must realize when you replace an injector on a Cat engine, each injector has a calibration code.  For this you do need a scan tool, or computer to change the calibration codes in the ecu.  What is the calibration code for? Basically its a number that represents how much fuel will be atomized in the cylinder and no injector is the same.  however if the ecu knows the calibration number it can account  for and adjust small discrepancies.