It doesn't matter what we think....your bike will tell you what it needs: If you baseline it and it runs well, and then you open up the airbox, add some K&N's, and you develop a lean stumble or detonation , you will need to look into jets and/needle spacers.
In a nut shell, a carb has three separate "areas" of control; idle/low speed running, controlled by the idle/pilot jet and slide cutaway; medium throttle, controlled by the slide height and main jet NEEDLE TAPER, and high speed full throttle, controlled by the main jet size...it's a bit more complicated than that, but it'll do.
As you make changes to the intake and exhaust systems, you need to examine the effect those changes make to each circuit. The most accurate method is the dyno run with an exhaust gas sniffer that measures burnt mixture results, but a decent tuner can tell a lot by "reading" plugs. It's an art, not a science.