Piper PA-46-500TP, S/N 4697349 factory equipped with Avidyne Entegra avionics. While doing the altimeter check per CFR 91.411 appendix E we noticed airspeed miscompare between ADU 1 and ADU 2 (about 20 knots around ground levels, about 5 knots at altitude about 20k feet). We have checked the R/H pitot system for obstructions - no faults found and leak test is also within limits given in AMM (less than 1 knot per 15 sec). Is there a way to calibrate the air speed indication in field?

You can do an ADU Calibration. The procedure is in the EXP5000 Maintenance Manual P/N 600-00141-010 Rev 6.  

Get into Setup page, then select Calibration page. Select the ADU and follow the on-screen instructions. You can do the ADU Cal multiple times to achieve the correct numbers.

If this is not successful, then the PFD will need to be sent back in to Avidyne.

Both PFD’s can be calibrated one at time, or both together if you have more than one Air Data Test Set.