Mitch,

The air pump on the M103 is a weak point. Specifically, the bearing in the electric clutch on the air pump is a weak point. No one will sell a replacement bearing and that is usually the failure point. Rebuilders revers engineer the bearing and get them in large quantities. I tried to get this bearing and even found the manufacturer in Germany but found the had an agreement with the EPA they wouldn't sell "user serviceable" parts to emissions equipment in the USA. You can fudge and get another bearing that is close and machine the clutch housing but you lose your ability to return your air pump for a core charge if they figure out you cut into it to make another size fit.

Good luck!