Ok, before everyone hops on this I would like to clarify things...

First off, don't worry your car isn't running lean, in fact its running right where it should be.

Now let me explain this, if you look at where your A/F ratio is 15.05 you are at 2500 RPMs. Your car is not going more than maybe 10mph. However, it is getting anywhere from 70-90mph of wind pushed into from the fans on the dyno...this is why you see your car leaning out at 2000R RPMs. Until your car is under full load (i.e. >3000RPMs) you can't really worry about the A/F measurement while you are on a dyno. If you worry about everything before 3000RPMs then you would have issues with how much hp/tq you are producing as well...just can't do it.

You have to look across the RPM band while the car is under full load. If you look at your graph you will notice that your peak A/F ratio is right around 12.8ish. This is just right, as the tail pipe sniffer used to determine A/F generally reads about .5-1 point leaner than it atually runs so your peak A/F is somewhere between 11.8-12.4. Don't fret. Everything is just fine with your tune and your A/F ratio. I'm more upset that the guy who ran your dyno for you did not tell you this if you brought up the A/F ratio while it was on the dyno...

Secondly, nice power/tq curve.