Go for a welded socket instead of a drilled and tapped hole in the dump pipe. There is not enough wall thickness to keep the thread from getting loose as it heats up - I know because I tried it and it failed - now have 1/4" NPT sockets, with reducing bush to 1/8"NPT in both headers for my EGT's and happy days. It cost me $50 for both sockets to be welded in at a local exhaust place and I supplied the mild steel sockets. You can buy the sockets on ebay. Check the size of the connection though as some pyro's have 1/8" on the probe and then have a special seating socket with male and female threads, hence why I have the 1/4" welded instead of going straight to 1/8"