Another idea if it's the pedals, not the cable that's causing friction is to install a light washer between the blocks to open up the holes slightly.  I got that idea from Orin Riddell.  I would start with lubricant, but if the blocks aren't perfectly perpendicular to the tube it could be binding.  I sanded off some of the powder coat to decrease the diameter slightly, mostly to get it smooth.

 

Mike Easley

Colorado Springs