[FerociousP]

I have to pass emissions in my county. There is a sniff test and a check for a cat (under car mirror check). I have started to finish the emissions on my t2 motor and learning the details of how the emissions system works I am less and less inclined to finish it to 100%. It seems the airpump, while providing some functions for anti-afterburn and driveability issues, takes air from the airpump and sends a small portion to the exhaust ports and sends the rest to the cat to aid in the reaction with exhaust gases. There is no EGR on S5 engines, so the only emissions functions are basically this air distribution system.

I have an RB downpipe to a custom cat center section with a RB catback. Will I have lower emissions by putting all the equipment back on and running the system "as Mazda intended"? Or, should I take all the equipment off and run the outlet hose of the airpump to the cat come emissions time? Will I see different results? Has anyone documented this?