My MPG has increased going from a 150ps to a 175ps CX5, both AWD. The only thing I noticed, and it is fairly obvious is there is a difference in the gearing. The 175ps has longer gears than the 150ps. In the 150ps I would often put it into 5th at about 35mph, that was about a comfortable lower limit for 5th, I would usually change to 6th at about 45mph easily. In the 175ps, 35mph gives lower revs in 5th and it isn't comfortable there, it needs at least 40mph, and then 6th is about 50mph. So it seems the gearing is longer, which is giving me better mpg.
Last few weeks of the 150ps gave me 40mpg with mixed driving, town and A road, some trips at full throttle here and there for fun, last few weeks with 175ps gave me 44 mpg easily, mixed driving too. I also think the regen duration is not quite as long, seems to last under 10 mins where the 150ps was longer. The high rev at start does not last as long either, maybe under 15s where the 150ps seem to go on for ever. I the shorter regen time will also be contributing to the mpg.
My 150ps had the latest update too so these difference were not expected.