Just thought I'd come back in and update the solution to my problem.
Even thought the air pump was replaced and I confirmed it was running (at least the one time I checked and listened for it), the issue was the connection to the air pump. The end of the electrical connector was ok and not noticeable deteriorated, but the ground wire was "rotten" up from the connector and the pump wasn't getting a good connection and therefore not running all the time.
Replaced the connection and all is good now. Just another thing to check...especially for intermittent problems.
Part numbers 61138352390 & 61130007569
I'm still glad I took the time to replace the back vacuum hoses. They would have caused issues before too long.