EPA FE testing is performed using the grade of gasoline recommended for use by the mfg.

If the HH.RX400 state that 91 or better is to be used, then it was tested with 91.

Tests are done with non-oxygenated summer fuel. If you are in a region with RFG, you will lose 2-4% due to the MTBE or ethanol oxygenate. Winter fuel gives you another 2% penalty or so. At 30mpg, that's a net loss of up to 2mpg in the lab...often more on the road.

Toss in the well-documents shortcomings of the EPA tests with respect to hybrids and much of your shortfall is pretty well explained.

Peruse the forums here and try out the techniques offered up- you'll be amazed how quickly you can exceed EPA numbers, even on 87 octane!