Reply To: Hello from USA.
Hello,
I do work on customer bikes yes in my workshop, besides selling parts.
The stock setup is perfect , as any tooth less on the front or tooth more on the rear is kind of 10% better on take off BUT you lose top speed a lot, they dont like screaming at top revs all day.
Better to lose the heavy monstrosity of the stock exhaust for something better. The only aftermarket exhaust i can recommend is the italian Leo Vince. Just search on Google “LEO VINCE HYOSUNG” and you will see it. Looks really good too! but expensive! , i believe it is on Amazon also.