Not a cobra, but I need some FE help

[d_ford]

Hey everyone,
I haven't posted here in quite some time since I sold my last ERA but I've been busy building a 68 mustang fastback with a 427 tunnelport engine. I finished the car and have driven it some but it has an issue I just haven't been able to figure out. It starts and idles great, drives very nicely as long as I accelerate slowly but as soon as I step down on the gas it starts cackling through the exhaust and doesn't really increase in power at all.
The engine is an aluminum 427 FE with alum. tunnelport heads and 2X4 intake. So far I have installed both new carbs from Pony Carburetors, changed out the pertronix unit in the dist. for points and condenser in case the pertronix was fried (it wasn't so I put it back), installed a pertronix flamethrower II coil, disconnected the vacuum hose between both carbs effectively turning it into 2 two barrels, advanced and retarded the timing, replaced the fuel pump, new cap, rotor, wires and plugs, checked float levels in carbs, and probably some other stuff I can't remember.
I was hoping with the vast knowledge base here on this forum someone may have additional suggestions or possibly suggest someone in the Ohio area to take it to. I'm about ready to give up on it. I've heard good things about Paul's Automotive Engineering in Cincinatti, anyone have any experience with them? I need someone good with FE's and multiple carburetion if I can't figure this out myself. Any help greatly appreciated. Thanks.