I took a look at PFF's signature stats but, the group all RB's for pass blocking. Leach was #41 with a 92.9 Efficiency rating. In 2011, he was #15 with a 96.8 rating.
There were only a couple of FB's, who I knew ranked very high in Hynoski from the Giants, and Ellison from Minny. The vast majority of all the RB's in pass protect was only in the range of 50 to 170 snaps doing so.