Alternatives for people who are savvy with sensors:
http://www.datatranslation.com/products/dataacquisition/usb/low-cost/Get sensors from Mouser.com. This will go 24 lines of high res analog.
The EGT sensor on late model Duramaxes is biitchin'. It will accurately read from 0°C to 1000°C (1800+ F), and yields 1-5v or ohms, I forget which. Basically, you can read it like a boost sensor. It is a thermistor? with huge range and accuracy. I feed the sensor into an unused emissions sensor line so I can read it via the factory ECM (shows up as EGR position?).
I used the DataTranslation thingy to try and map out cylinder pressure in real time on my engine, and tie it into the injection event. Also to see spikes in fuel rail pressure. It's primitive but really flexible. And fast. It will capture the pressure curve of the combustion event in detail.
Not for the beginner, but if I can figure it out, I'd imagine most can. I knew nothing about electricity other than how to injure myself when I started doing my own datalogging and sensors.
About EGT vs O2 on a gasoline engine? IMO, O2 hands down. EGT has too many variables to be useful, it's a "I dun blew it up" sensor. In my experience lag time on conventional thermocouple (microvolt) sensors is pathetic and unreliable. By the time it tells you #4 hit 1800F, the damage is already complete. That being said, I do run EGT data.
Your results may vary, offer not good in Alaska and Hawaii, do not attempt this at home, if you have an erection that lasts more than 4 hours, you must have driven the new CTS-V.