I think you can do all 4 without removing the carbs. Don't count on the shims helping anything. They didn't on mine.
I've seen people say it does nothing at all and some that say it's the greatest thing since sliced bread. It should be simple enough to try though, if I have time to get to it. Worst case, just pull the slides again and remove the shims.
I'll also look into ditching the paper filter - I'm not sure just how old it is, clean-ish or not.