the OEM RSS setup was part of the ulysses comfort kit. all parts still available and to answer your question....YES...it makes quite a bit of difference. the more air you can funnel into an air-cooled motor particularly around the cylinder head and exhaust port area the better off both you and your XB will be. it's money well spent. every single one of my XB's receives these parts.
here's what you'll need. either have local dealer order up or order online. all items still available.
any H-D dealer can order for you or try online sites like surdyke...lancaster H-D...new castle H-D
numbers and quantities as follows:
inner scoop....quantity 1....# M0852.7AA
outer scoop....quantity 1....# M0851.7AA
attachment screws....quantity 3....# AN1005.3FSS