[Jdub]

My understanding is that the smog pump simply puts o2 into the exhaust after the fact, at the (is it?) post-header point. That would mean it would not effect the CO2 at all. Of course, I am talking from an SC perspective here, so unsure if your 89 is like this at all...

Those who know should chime in. You could always put the belt on and do a before and after CO at a local garage. Do be sure to replace the filter in the smog pump so you get all the air you'll need.

John