Why can I not go any faster?

I have that same carb.

I removed the butterfly choke valve on the secondary to get more airflow andit still starts fine in the morning. of course I live in the desert and it gets 30 degrees as the coldest. so it may affect in colder climates.

I took the old hedder of my 62 chevy truck and used the elbows to weld an intake for a k/n type filter. each barrel has its own tube feeding it air. these join into a bigger tube which receives a tubular filter. I can feel the rush when I accelerate.