It certainly does sound like fuel starvation. A question though....why are you using 2 fuel pumps and 2 in line fuel filters? One of each should be more than adequate as long as the pump has reasonable capacity. Electric fuel pumps normally work better as a "pusher" rather than a "sucker". It is better therefore to mount the fuel pump down low and close to the fuel tank to minimise the length of suction. The filter is best mounted in the pressure side of the fuel pump (between the pump and the carb). Old morries have a small diameter fuel line as standard and they are also suseptable to getting squashed. I would replace the original fuel line with a new bigger line (at least 5/16 or 8mm). Make sure the fuel tank breather is not blocked. If you can, mount a tee joint at or close to the carb and fit a fuel pressure gauge in the line. That way you can tell whether you are getting a fuel starvation problem before the carb. If the pressure remains constant without dropping off at full revs then the fuel pump, filter and line are ok. If the engine still appears to starve at full revs with good fuel pressure then you need to look at the needle valve area. Fuel pressure in the area of 3-6psi should be adequate with a standard carb.

I hope this helps :)