I can't help but wonder, are you comparing how your skin feels after a single wtg pass to a single wtg pass. It could be that you whiskers are laying against your skin and are not being taken very short while doing a with the grain pass. Trying a small test of across the grain might prove or disprove that, also checking you double edge shave while shaving and observing how the different passes are working on your whiskers. All of our whisker growth patterns tend to be a little different so a refined technique will vary lot from shaver to shaver. Don't be afraid to try different things and I'm with John 3126 on the possibility that your lather may be too dry for a straight.