In decades of engine building, I haver never seen a 0.010" spread [ 0.010 int, 0.020 exh ] in valve lash for a street engine. Usually 0.004" at most. If the correct lash is actually 0.020" [ likely ] for the intake, then your comment about the feeling of extra load on the engine makes sense. The tighter lash increases duration, & at low rpms [ lugging ] that often reduces torque, making the engine feel sluggish.
