Aftermarket mufflers present problems for the 90 size two strokes.

In most cases a 60 size will bolt up to the engine but they don't have enough internal volume and will cause over heating and detonation.

Then some of the true 90 size ones have the internal volume but do not have enough back pressure for good tank pressure and resulting fuel draw.

I just wanted you to be aware of some peoples experiences. I'm not trying to single out your choice. I am not familiar with yours.