[mark houghton]

Just to chime in on another option, though not necessarily the best. I put mine post-muffler, as far in from the end of the tail pipe as possible (about 10" in my case)....at the risk of erroneous lean readings at idle due to low exhaust volume and the possibility of ambient air sneaking in. Once past idle it seemed the gas volume was sufficient to preclude any exposure from ambient air and my readings were steady. Even if the readings weren't entirely accurate, at least it would err on the safe side reading leaner that actual if it was picking up any ambient air.

Again, not optimal location but it's what I did for what it's worth.