got a 2010 35hp CDI GDSD. Wanting a little more umph for the loads I carry. Runs 24-25 with just me but with 2 other guys I'm down around 20-21.

Got a motor head buddy with a shop and he says he can do the headwork for me and that I will see the most gain there. Probably won't cost much at all for him to do this for me. Can I do that first?

It seems like the first place most people go is Mikuni and aftermarket muffler.

These new mufflers on the CDI seem to have a more deep throaty sound and I'm wondering if they aren't close to what the aftermarkets are providing.

You can do headwork before the carb. I would add the high flow exhaust when doing the head work though. An aftermarket is going to flow considerably more than the stocker.

Headswork give you da most gain as for as any single mod done.

Brand new engine --- protect your warranty ! ! !

Keep all your original parts in original condition --- just in case
you can put them back on after it goes BOOM ! ! !