Dismiss air injection as a problem. The air pump operates for a minute or two on cold start to get the cats going then they're dead weight and belt drag for the rest of the trip. Once they disengage they don't contribute to the emission control process.

I'd like to know if it will help during emissions testing to leave the air pump engaged...

Sixto
95 S420
91 300SE
87 300SDL
83 300SD