This site has a lot of info on intakes and how they flow. I put a T hose connecting the carbs to keep the vacuum equal between the 2, I put it on the main large inlet and T off to each other and then to the PVC valves. I'm going to change it to just the 2 carbs and put 2 cover breathers on each Valve cover, it works better that way. I changed it when I built a 427 sbc thinking it would look better, but it sucks a little oil and in turn it puts deposits in the chambers. On my 406 I had 2 breathers on each and had no problem. On the hottrodders site woodz428 gave some good info. I think the hose will help quite a bit. You can jet down 2 sizes to help. Also check the throttle blades between the 2 carbs, to see if one is open more than the other. I had this problem on my cross ram. On the float settings I set them so you have to rock the car to get them to dribble the gas out and having the front a little lower than the rear because of acceleration.
Holly Carb site has a free downloadable manual and a trouble shooters guide which is very helpful.
I hope this helps you. If you take the bowls off check the power valves, use a hose and blow to see if their bad, I usually use 4.5 in all my carbs, and 99% of all the carbs like 3/4 turn out for the vacuum setting. A small air cleaner will make it run rich also. A K&N 6" X 2" will only flow 275 CFM according to K&N when I talked to them (FYI) . How does it run without any air filters on it, and what's the idle? mine is 550 rpm and I can put it down without any problem. I do get some black smoke once in a while but I found it was the rubber from the radial tires. I hope this helps you in some way.
Please stay in touch.
<a href="http://www.holley.com/HiOctn/TechServ/TechInfo/TechInfo.html" target="_blank">http://www.holley.com/HiOctn/TechServ/TechInfo/TechInfo.html</a>
<a href="http://victorylibrary.com/mopar/intake-tech-c.htm" target="_blank">http://victorylibrary.com/mopar/intake-tech-c.htm</a>
By the way your email does not work.
Luv the smell of NITRO in the morning.