[Dead Parrot]

Not an expert by any means.

What does Howards say that cam's rpm operating range is? You could be chasing performance in a range that your build isn't going to provide.

Until you open the back barrels on a 4 barrel, you have a 200~300 cfm carb. A larger carb isn't likely to solve your low and mid range issues.

What is your idle vacuum? Might not have enough to kick in the vacuum advance.

Ask your mechanic how many miles it takes before the rings fully seat in. You might not have a good seal yet and lower then expected cylinder pressures. Yep, another vote for let it get broke in a bit more.