Red is silicone to fix air leaks, no worries about that.
For CNG setup, you either need Venturi or drill the carburetor. You have venturi installed. The metallic thing where your cng pipe connects on carb is venturi.
Drilled carburetor has CNG pipe connected above fuel idle mixture screw, like this.
Did you re adjust timing and cng setting?.
Search ' venturi ', ' jerk', ' jerks ',' hiccups '. You will find some very useful posts.
Your car is missing CNG kit coolant pipes, to heat the CNG kit, for maximum efficiency.