I own a 91.
Better keep it as stock as possible. The KN filter won't make much difference one way or another, real advantage is durability, as is rewashable. If you want to go one size bigger on mains, that is OK.
Don't understand question on pilot jets, as they are #35 stock, and if you want to go to #38 that's OK. Hopefully you are aiming to preserve, and not for 'power'.
'Rebuilding" carburator is nothing else that replacing rubber parts, and thoroughly cleaning (assuming no mechanical damage) Thus you should replace the tiny O-rings in mix screws, the float needles (or valves), and bowl gaskets. Hopefully the diapghragms are OK. You could replace the phillips bowl screws for Allen, they are easier to take out.
...If you are in the US, you would have to remove the mix screws expoxied lids, if not done yet. Parts are available of course in on-line microfiches as Keihins CVK32 were used in many motorcycles, but if you know what you want, you can go to to dedicated sites selling parts for Mikunis, and Keihins....or go to Ebay, they would include parts in their 'kits' you may not need and only require cleaning, but is up to you.
.........very likely the petcock is leaking too and may need replacing or refreshing with new diaphragm.
