Pre Turbo is best, and at the "Y" is where I installed mine. Cummins12V98, his 4th gen is running Edge Juice with attitude with the CTS2, as soon as you change any programing on the 6.7 for any year/HP/TQ, you must monitor the true EGT. If your not going to use the truck capabilities to the max, then maybe, but if you tow any kind of load you need to monitor EGT. Boost is also important due to the fact head gaskets are known to fail on the 6.7 that have other than stock programing, although it's mostly due to EGR removal.
LLucas, are you seeing the boost the 6.7 reports through the OBDII, or do you have you an independent sensor?