This could be a really silly question, but...

Went out for a drive a while back with Brant and used his wideband air/fuel tester to get a base line on how my 76 2.0 air/fuel mixture looks. Edit: Totally Stock Djet 2.0

We were getting readings close to at about 13.3 to about 14-14.5 at cruising/load.

I know that is a little lean, but my smog pump is working, so wouldn't that trick the readings, and my actual is richer than whats read at the tailpipe?

Does my logic make any sense?

Ferg

Yes, possibly. Ferrari's of the 80's had a sampling port in the exhaust ahead of the catalytic converters and the air pump injector. You unscrewed the cap and inserted the AF meter probe. I barely recall the function of the air pump was to deliver air into the exhaust until the cats warmed up. Then at a certain temp a device diverted the air from the pump to atmosphere to keep the cats from melting. The whole system was basically a GM design. Ferrari quoted the airpump in the several hundreds of dollar range but the 1983 camaro pump was exactly the same for 39$ at Pep boys. LOL. I'm thinking your airpump operates the same way, but not sure?

Here is an article on their function Smog Pump

Non CA 76 so no CAT.

I assume the pump is injecting air all the time no?

Why don't you do two tests the same day. Do a 15 minute drive with the system the way it is and record your readings. Then remove the belt driving the air pump and do the same drive. Report back to us the results.

Was thinking next time I'm at Brants may just do that.

First I need seats. They are out for new tartan inserts, hopefully in two weeks.