I LOVE THAT AFR CURVE!!!
What kind of gas? 11.7-11.9 may be just a hair lean for 91-93 pump gas. How much timing were you getting during the run? Low timing can greatly reduce power numbers. Your power curve should be pretty smooth, but yours is jagged and uneven. I'm guessing that you may be knocking, causing drops in timing, either due to too much timing, or possibly a little too lean for the gas you are using.
More info needed and the DSMLink log if you have one would be awesome!