interesting. any corrections entered for drivetrain loss (ie, this is actual wheel hp and not wheel hp adjusted to flywheel hp)?
otherwise, i would not worry about the afr readings - from what i've read, if they did the sniffer up the tailpipe approach the readings are not accurate; here's a quick search result:
tailpipe vs. wideband?
finally, looking at that 5500 rpm dip you have. i am trying to get my head around it. truegearhead had something similar. you see it on occasional dyno results. it may be an effect of scaling, as it shows up on the factory dynos also - ie, it just looks worse on a dyno that has an exaggerated 'y' scale. what is happening at 5500 rpm? the resonance tube closes again (opens at 3000 rpm, closes at 5000 rpm) and the variocam returns timing (advances timing at 1500 rpm, returns at 5500 rpm).
https://www.6speedonline.com/forums/996/205309-how-variocam-variocamplus-works-primer.html