Hi, Bryan, I understand what you're saying about non genuine parts and I normally only fit genuine or Bosch etc. but I was not 100% certain that this would be the fix but in this case I was able to return the part if not required.
It drove exactly the same and I refitted the original MAF.( The part was absolutely identical in all physical ways though as explained above.)

The fault was general lack of performance up hills and overtaking.

Yesterday I found similar previous post on here, the FIX was 2 new brake light bulbs....?
I rang my customer to get them to check the brake lights - both blown but high level one ok.
Replaced blown bulbs and the cars performance was restored!!!
Apparently this is known by Nissan but they don't seem to know why.

Thanks, Martin.