.......always been the same motor throughout it's production?

I ask because I have one bought from an Aerus dealer, and I liked it so well that I bought another one via Ebay. The machine arrived today, and all looked good with the machine, until I powered it up and immediately noticed the motor didn't sound the same - it sounded like the earlier Lux motors. The Guardian upright motor on the Aerus obtained machine has a noticeably higher "whine" and much stronger suction/airflow. The Ebay motor runs smooth, but it's obvious to me that it's not the same.

So I then take out my Electrolux ball suction kit and test the Ebay machine at issue, and it tests just like my Legacy upright does. So I'm thinking one of two things happened: One, the motor changed throughout the production of the Guardian upright, or two, the motor was swapped for an earlier one.

Anyone enough Lux knowledgeable to know if the motors in the Guardian upright changed, or did I get an incorrectly serviced machine?

.....and found out that there WAS an earlier motor in the Guardian upright. The high rev/airwatt motor is more recent. For the benefit of the forum, I can tell you that there are definitely two versions of this machine - an earlier motor, akin to the performance of the Legacy, and a higher rev/airwatt version that's the best performance upright they have ever built. Since I found out the hard way I might as well share the knowledge with the forum and for the archives.