The throttle tube resistance doesn't bother me as I always manually turn the throttle back to idle; my problem was my carb throttle levers were returning slowly to that point, much more slowly than my handlebar throttle.
I wish I knew where to find pictures of the older and newer throttle covers. Mine has a protrusion but it's more like 1/8" to maybe 3/16" down, not 1/4". Luckily for me my local dealer doesn't charge me a restock fee. :-)