Many sites mention that you do not need to replace your air filter with a K&N with purchasing new exhaust. Is this true? I have also read that you do not need to remap your bike after placing a slip-on pipe; however, it would provide more performance.
The way I understand it, if you increase the flow thru the exhaust, you should want to increase the flow through the intake... However, if you do not mess with the intake, I believe that most slipons do not require the FI to be adjusted... I believe that when you "open the air box" and do slipons, people recommend K&N because of their durability vs. standard paper filters... and that with open air box and slipons, then you would "need" to adjust the FI system.
that's pretty much it... adding slip-ons allows the bike to "exhale" better but the intake is still quite restricted with the stock lid in place. so to take advantage of the superior exhaust flow, many opt to open the airbox as well to have "matching" intake. when this is done, the air/fuel ratio has to be tweeked via rejetting (carbs) or remapping (FI).