Smog / Airp Pump output???

[ACCD]

Hey guys, I tried to search for an answer but couldn't find one.
I've got a 93 300ce. The check engine light came on, took it to a local dealer here in Dallas. The diagnosis was "your air pump isn't putting out enough air volume"... Well that was a first for me... I was thinking 02 sensor or something. Obviously the dealer wants $1,300 for a new MB pump.. I picked the car up and am on the hunt for a rebuilt pump.. however the check engine light hasn't come on. I didn't know that an air pump could wear out in 90k miles.. bearings yes, volume no...
I've had this car 14 years and it's driven gently with only 93k miles.

Any thoughts??

Thanks,,

PS.. Just new to the forum and I must say, Lots of great info and knowledge, thanks in advance.