Here's a couple of pics to show the ideal location for the EGT pyrometer probe to drill and tap in the manifold
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this pic shows the EGT fitting centred between a couple of webs on the manifold, just above the turbo flange
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I've drilled this so the EGT pyro fitting is just clear of the radiused internal corner at the flange
it fits nicely equal distances from the raised castings on three sides
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this shot shows where the threaded hole comes through on the inside. You can see the rib in the centre that directs gasses from the front and rear manifold section toward the turbo. drilling the hole for the pyro any higher puts the probe into the dividing rib.
it could go maybe 1/4" higher before it was a problem
Tapping a tapered thread is kind of scary, it felt like the tap was going to break so many times. It took a bit of trial and error to get the drill size right so I finished with a tapped hole that let the bung screw far enough in and seal without bottoming out on the manifold