A very, very complex field that essentialy is governed by what you "need" from the EGT indication. By that I mean for example turbine engines where 980 deg is eco cruise, 1020 is max cruise, 1032 is sprint and 1072 melts the engine so a matter of a few degrees affects speed, range and engine service life.
A turbine engine may have up to 32 probes in Inlet to get the absolute optimum reading it is so critical.
Sooo... what about a Patrol? Well, pre turbo will give the best indication of the combustion temps which is what makes or breaks the engine but is it that big a deal?
IE are you looking for temp limits or history to decide if the engine needs to be pulled down because it is being operated up near the raggedy edge and it went over the line for too long or too often before you melt a valve or whatever?
IMHO, for a reccy vehicle like a Patrol post turbo is fine. We err on the side of caution with the post turbo peak sustained EGT's anyway.
What nearly everyone is looking for is 1 of 2 things. Either an unusual drop/rise in sustained temps indicating something is wrong like a MAF fault or whatever... or... a normal operating range such as if the EGT is rapidly rising and looks like going north of say 500 degrees you back off or change gears to reduce load.
Bottom line, purely IMHO...
If you want to know the actual peak combustion temps then pre Turbo for sure.
If you just want to operate the engine below a level where the risk of damage from high combustion temps is dramatically increased, then post Turbo is fine as well as cheaper and easier.
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