could the intake be holding my low end down?

Addendum for street use;
170psi, now we are into aluminum heads, and things are heating up
180 is 87E10 friendly to save you several thousand dollars over the life of the engine, and incredible throttle-response, great fuel mileage is also possible.
190 is AJ approved,for best pumpgas, and makes a tire-eating monster. It may run on 89
200 is the Mitch-approved, probable limit for 91pumpgas. I haven't been there, cuz honestly with a manual trans,IMO; there is no way to tame it with street gears; 185 is tough enough, and cannot, IMO, be done properly with just a dizzy. If I were to try it, I would want a stand-alone timing computer.
There are only a handful of FABO fellows who responded to a question I posed a year or two ago, that dare to run this high, and reported success.

How do you know unless you really try it?

My last combo ran at 185 psi with closed chamber heads 302's and it was a monster. It was still making torque at 6k where it hit the limiter.