You won't. (Get a good reading. The install destructions warn you about problems too far down into the collector of tube headers, etc. Not only does the sensor need to be hot, you can't have atmospheric air contamination
So I take it then that there's no sense looking for a tailpipe probe. Any chance you could recommend a decent semi-portable meter that won't break the bank? - Maybe a handheld that I can use with probes that I'll have to move from car to car (realizing that it now sounds like I'll be welding bungs in each vehicle)