Not sure this is the right spot for this post, so moderators/admins pls feel free to move it to the correct portion of the board.
I just installed the fan diffuser that Yoder provided to me as a warranty upgrade to my pre-5/13 YS 640 (free of charge, by the way--Thanks Yoder!). FYI, the install is extremely simple. Takes no more than 15 minutes and requires only a phillips head screwdriver, a 5/16 nut driver or socket or crescent wrench and the provided diffuser and 2 nuts and bolts.
I'm just curious what this mod is supposed to do? It obviously redirects air flow from the fan next to the outside wall of the pellet hopper, but I'm just curious how that will impact both side to side cooking temps and pellet consumption? Trust that it does, just curious on the how or why?
Thanks to Yoder for continuing to stand behind its products and customers. 
The rear fan diffuser was added to the low CFM fan for two purposes. The main function was to prevent the high CFM fan from super charging the outer fan. This would cause more air than required into the burn pot and cause the unit to have a hard time heating up and consume pellets at a higher rate than necessary. The second purpose was to cool the hopper and all components. The added air creates adequate circulation through the inside of the hopper to keep the components within acceptable temperature range.
Thanks Herb and thanks to the folks at Yoder too! Appreciate the helpful explanation and very psyched to see the 640 in operation w/ its new diffuser installed:!: 
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