Sounds like ya just need to find the correct main jet for your local atm pressure. I have the SHA 15.15 carb on my 66cc Grubee, and it works great. Truth be told, this carb is kinda pricey, but works nicely. I ended up going down to a #64 5mm main jet. I'm @ sea level, on the coast of Maine.
I would not recommed it for stock engines, it's 'almost' to big.
I found out my restriction was air, not fuel. Just for fun, take off the air filter and cover. Does it run better? If so, you need to go down in jet size, or allow more air to flow through the engine. Going up is not always the answer, you are seeking the correct mixture.
I ended up taking the air filter out, and drilled small holes in the cover for less restriction, made a big difference.
Sick Bike Parts sells the 5mm jets. I'm pretty sure that's your problem. If the CNS carb works good, the SHA should work better once dialed in correctly.
Good luck