Thanks for the kind words, I get that things can be cheap for a reason, but isn't that the allure? Take something centered around economical transport and squeeze every bit of performance out of it?
I haven't had a chance to try anything yet because I'm also renovating some rooms in the house, but if my experience with motorcycles has taught me anything, I'll have to re jet this all in the summer anyways, because 35f is a lot different than 80f.
As far as the air filter goes, I think I'd prefer using a foam pod over the screens, and I'd be willing to go to a carb with more than one circuit, though I doubt this engine needs that much tuneability.
I did leave the grease in the crank bearings that they come packed with from the factory, so that could be introducing some drag until it finds its way out of them from the oil air mix thinning it.