Mine is located in the exhaust manifold just before entering the turbo. That is the recommended position.

I knowe most recommend putting the thermocouple before the turbo but--did you weld in the bung or just drill and tap? On the 5.9 the exhaust comes into the turbo split between the first three cylinders and the last three, it is only in the turbo where the exhaust is combined.

I just replaced my manifold the old was cracked and I did look it over carefully for a good spot for the thermocouple, do you have any pictures of your installation?

On some of the Dodge sport truck sites they recommend to add 300 degrees to the reading if the thermocouple is aft of the turbo. Will do more research on this, I don't have anything done to my engine, completely stock, will be looking to change the turbo housing to #16 later this year. Will greatly improve the turbo spool-up!

I drilled and tapped mine with the manifolds off - 1/4" NPT is the standard.