EGR is exhaust gas recirculation.
AIR is air injection reactor.
Egr takes soem exhaust gas and reinjects it into teh intake manifold to reburn it.
AIR injects extra air into the exhaust so the exhaust burns more completely in the cats.
You probably have EGR, most Cali trucks have AIR. If you have a bunch of silver looking tubes running into your exhaist manifold you have AIR.
Underthe hood tehre should be a stiocker that tells you whether or not these 2 emissions systems are prsent or not.
I woulnt waste my time with shorties on a NBS truck, if yiou want bang for buck, longtubes all the way.