New clone possible fuel issue

I just finished up a duromax clone install. I purchased a carb from VC so I could adjust mixture if need be. It's like it has a miss. It also does if going uphill. I tried turning out on the air/fuel mixture and it didn't help. I also tried adjusting the float but no luck there either. I went ahead and put on the original carb that came with it. Still doing the same thing. I have a car muffler on it so wouldn't think exhaust would be restricted.

Any ideas?

Thanks!