Depends what you want to measure.. Technically you want it before the turbine, so you can measure the turbine inlet temperature.. but some people are worried about TC probes breaking and damaging turbos (never seen it personally).. If you put it after the turbo you have to factor in the temperature drop across the turbo.. So perhaps you could measure it before and after and then remove the pre-turbo sensor if you're worried about breakage.. at least then you KNOW the drop across the turbo