2001 2500 HD 8.1L Scary AFR Results
 

My fully stock 2500 HD 8.1L (62k miles) seems noticeably down on power at 50%-100% throttle. I decided to put it on the dyno.

Max HP = 230
Max Torque = 277
Air/Fuel Ratio = 16-18 from 3000-4700 RPM (YIKES!)

I have no idea why this is running so lean. After the dyno session, it tripped a P0100 code ((MAF) Circuit Malfunction), but that cleared within about 10 miles. No other codes have been reported since I've noticed the lack of power.

If the AFR is correct, that's why I'm down on power (I'm trying to ignite air!!!).

Any thoughts or suggestions are appreciated.

Maybe cleaning the MAF will help it.