weber carb problem

[chris.S]

hello i have been having trouble with my van and need some advice
it idles well and rund ok till it kangaroos and then dies only above 30
so far i have done as follows

read the wiki on carb faults ect
found no induction leaks
no air pockets in the fuel line
fuel filters fine
ignition all fine
carb stripped and cleaned ALOT
good air filter
and i have vacume

this is starting to break me a little
but wehn stripping the carb i noticer that the accelerator pump
(no 7 on here) http://www.gowerlee.dircon.co.uk/DFTMtype.html" onclick="window.open(this.href);return false;
is a diaphram with a return spring now
this is returning slowly and i mean slowly could this be the cause of all my problems a dud diaphram and spring?

im so near the end with things to do i hope this is it.

[chris.S]

oh and it ran fine before i removed the carb whilst i was fitting new gaskets the carb would of been sat dry for 2 and a bit weeks