Where is the A/F graph?

Got it...the black one.

Well, my friend you have a problem. Your car is running way too lean and that is one of the reasons why your peak hp comes so late.

IMHO your peak tq point should be the richest portion of the a/f graph. In the range of 11.4:1 for a street car that is tuned. From there you can lean on it alittle say to 11.8:1.

A safer tune would have you 11.0:1 at peak tq then tapering to 11.5:1 at redline.

You better look into why the readings were so lean.