trouble with ignition

[unimog406]

I think. the symptoms are: the car burns lots of gas [approx 4 mpg], it is very jerky below 3000 rpms, especially when at part throttle and starts breaking up above about 4300 rpm's. it is a 66 911 with weber 40ida carbs that I have gone through 5 million times. they are slightly rejetted, but not dramatically. all accelerator pumps are working, no gas is dripping out when the fuel pump is on, but car is not running. the fuel pressure is about 2.5 psi. the ignition system is brand new, it is a new 40000 volt 3 ohm coil from pertronix [model number 40511] with a pertronix hall effect ignition [model number 1866]. it has a new distributor cap, new wires, and new plugs [ngk bp5es]. We recently took the car to a local porsche mechanic who came to the conclusion that our carbs were working properly, but we were simply not getting enough spark. we will foul a plug on occassion, but typically they just come out looking black[as opposed to brown-tan]. we have played with the carb some trying to lean it out, but the farther in we go, the worse it idles. the porshce mechanic is familiar with webbers and tuned them himself.
having talked with some folks about this it seems that the capactive discharge box that came with the car [the last owner added] will not work with my hall effect ignition, but they reccommend an ignition box such as an msd or a mallory. have people had luck with these? does this even sound like an ignition problem, and if so, what would you do?
thanks for any advice,
Bob