lol... good ole duck.
very simply, there are 3 parts to the carb jetting. the idle, midrange and top end. the idle circuit is handled by the idle mixture screw and the pilot jet. the midrange by the needle that we are talking about shimming and the top end by the main jet.
the idle circuit and midrange are lean from the factory. instead of doing both, we are raising the needles with the washers to richen where the needle comes into play with the idle circuit. By raising it, we let in more gas/air mixture earlier when we turn the throttle, which in turn makes more power. the net effect is that the bike's power feel "fatter" from right off the bottom.
On the other hand, the stock 98 main jet is a bit too rich from the factory, so pulling the snorkel out actually leans out the bike a bit and makes the 98 main just about perfect for the top end.
Pulling the snorkel, though, will lean out the mixture from idle to top end and the idle and midrange will suffer if you don't compensate for it by richening the mixture by shimming. That is why in my DIY on pulling the snorkel I recommended only pulling it after the needles were shimmed.
The best time to remove the snorkel is when you do the shimming.
On my bike, with an area p QC exhaust, I ran with 3 washers under each needle with the snorkel removed. It ran fine in that configuration and at no time did the top end suffer from being too lean with the stock 98 main jets.
The above advice is all with you using the stock airbox. If you remove the airbox, everything changes.
Do it, you'll be fine.
