Same engine as my DT. It's common to remove the snorkel but it won't get you anywhere power wise, just more induction noise.
As regards jetting, I ran a Big one system on mine and more recently a DEP with stock jetting and that was fine. I'd recommend returning the air screw to standard setting and see how it runs then. I think it's 1 and a 1/4 turns out from lightly seated.
It would be worth checking the powervalve alignment too.
For the earth of the green/black wire I crimped a ring terminal on it then bolted it to the radiator frame.
Mine tops out around 75mph with a 1