Well, it's the floats that control the flow into the carbies and therefore also the pressure. So that might be something to look at. (As well as the needle and seat)
There have been bad batches of floats in circulation for a while and I thought it had been sorted but a local Vixen with several hundred hours was found to have bad floats recently.
The flow to the fuel pump in not impeded? No blocked filters, kinked hoses? Disconnected at the pump inlet side, the fuel flows readily out the hose from the tanks?
Tank air vents clear?
Any sort of restriction on the suction side of the pump, alows the posibility of vapour being pulled from the fuel.
As a long shot, the carb vent lines? Generally they give mixture issues if poorly placed in pressure/ vacuum areas.
If using a sealed cold air intake, they should be attached to that.
How are you measuring the pulsation? Definately no suspicion there?