I just ordered an AFR gauge and also a "no weld" fitting which wraps around the exhaust to install the sensor. I am planning on buying a Lindsey 3" system in a couple of months so I got the no weld fitting for now.

Question: since the stock 1987 951 exhaust is double walled where should I drill to get a good reading?

Many thanks to the RL brain trust.

 

The double walled downpipe is of no consequence as the sensor is not installed in the downpipe. The heat and pressure there is too high and would quickly kill the sensor. Most people installed them in the cat pipe at least a few feet downsteam of the downpipe.

 

This is the correct place to install a wb02.
http://www.lindseyracing.com/LR/Parts/WBO2LOCATION.html

 

Thanks all - the instructions do say to mount the sensor "downstream" on the exhaust especially if the engine has a turbo. I think I am going to mount it on the cat pipe until I get my Lindsey exhaust.