What is wrong with this combo

60' are missing about .10-.15 depending on where in the 1.5x you are.

Try to get a good known carb and try out like Demon suggested. Lots of "trick" carbs are total junk.

Make sure the timing is set to optimum. Get the basic set up right, MPH.

Wouldn't be the first time those heads don't work like the numbers suggest.