Rick, follow your headers along (I don't know your particular model) you
probably have two and where they join, to a single exhaust pipe you will see
the little bugger sticking up... often there is a bit of an aluminum shroud
for protection which may have prevented you from seeing it.

By the way, I need to do same for my 300E ... hate getting underneath the car
and ramps seem like a good idea.  Last time I tried it though, the ramps
simply kept sliding forward on me.... how do you get the car up there?

cheers, guenter

If it is like mine, it is on the right side exhaust pipe just as it comes
out of the exhaust manifold.  It is on the top of the pipe and hard to see.

If you have original cat. you will have two of them... big one is obvious...
and then there is another smaller one by the starter... closer to engine.
You should see a wire there going into the middle of the smaller cat.