i use the tech edge one,

only reads probertly in down pipe to mid section, b4 any joints,

in tail pipe dont read accurate at all on idle or cruise, but does on full go, i,ve tried 75mm-20mm tail pieces, 20mm is best, but cant beat in down pipe.

but to close to turbo, will over heat the sensor (over 850 dee C) a nd it will read rich, as i believe why my cossie melted, the sensor was fitted 20mm from 3 bolt flange on down pipe.