Shortline know his stuff, so try the 300EX.
But, if you already have a 350X carb, it seemed to work great for me. I have a Supertrapp and an open air box with an 11:1 piston 2mm oversized, so I didn't have a ton of jetting to do.
It worked out very well for me.
The nice thing is that the cold start problems disappear with a different carburetor. If I recall correctly, the choke lever hits something and I had to bend it and or remove some material with a cut off wheel.
I used a heat gun to get on my intake.
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country