Greetings & Salutations!!! Welcome to Ninjette!!!
Mufflers don't do much on this bike for performance other than weight-savings. It's headers that make biggest gains; Tyga has highest power with their full-exhaust.
For mufflers, I played around with several aftermarket versions and modified their innards. What works best for noise-reduction with straight-through design is to have larger outer canister. When exhaust enters muffler, it expands through perforations. The more the expansion, more pulse-pressure variations are absorbed. Expansion also cools exhaust and shrinks volume. This draws flow back into centre core in 2nd-half of muffler and out rear. Also fill gap between inner core and outer chamber with fibreglass or stainless wool packing material.
I would try larger outer canister with thin wall-thickness. Aluminium or CF would give maximum weight-savings. The larger Tyga muffler was definitely quieter than smaller el-cheapo muffler I got from Ali. Smaller Ali muffler weighed 1390gm while Tyga
with my Laguna Seca elbow weighs 1620gm.
Some photos and discussions here:
https://www.ninjette.org/forums/showthread.php?t=307767
https://www.ninjette.org/forums/showthread.php?t=338180
Good articles:
http://www.vaglinks.com/Docs/Misc/Mu...t_Section3.pdf
https://www.researchgate.net/publica..._vehicle_Noise
Might also consider cutting off kickstand bracket. At some point it will dig into ground and cause crashes. Great job on bike, your son is so lucky!
