which is better, and does the tubo have to come off to be drilled? ???

 

Since you're concerned about heat (and too much of it), mounting it pre-turbo will give you a better indication of exhaust gas temps in the engine.

Mounting it post-turbo will allow some heat loss to occur in the turbo before your sensor, leading to a lower reading and possibly misleading information.

I don't think the turbo has to come off, but I would be concerned about metal shavings making their way into the turbo.

 

Mark,
There have been some great discussions on this site about pyros, where to mount, why, etc. You would do well to run a Search and see what is there. Also, send a PM to Push Rod at www.wildcatdiesel.com *. He will guide you thru the process.
Bob

* edited to correct info

 

I mounted mine post-turbo because all I am concerned about right now is cool-down temperature of the turbo. Pre-turbo won't tell you as much about that. Someone made the analogy that pre-turbo is like monitoring the tip of the torch not the piece of metal it just heated up. I figure if I ever decide to do some bombs I can put a 1/4" plug in my post-turbo hole and drill a new hole in the manifold.