help with running problem

hi,
i'm hoping someone can help me.

my cab developed an intermittent running concern when i changed my pierburg for a weber which has continued to the point where i have tried  / changed everything that i can think of although nothing has worked so far and i am stumped as to what it could be.

Work done so far:
New Weber conversion - manual choke
new fuel pump (mechanical)
New stainless steel filler neck
New in-line filter
Full electrical system check and tuned by local tune up specialist
Fuel lines blown thru
Sender removed cleaned
Fuel tank checked - clean

Cab starts ok sometimes good flow of fuel into in-line filter sometimes not and can be driving ok but suddenly seems to lose power wanting to stall and kangaroos needing high revs just to pull away without stalling.
Now parked on drive and idling with good fuel flow but lumpy when accelerator pressed quickly and wants to stall if trying to pull away in 1st gear.
The only thing which i haven't tried is the gravity valve could it be that or does anyone have any other suggestions because i've hit a brick wall and it is driving me mad cos the cab is also my daily driver.

Cheers for any help -i'll try anything

Docc
  

with it ticking over spray copious amounts of easy start over every single join in the inlet system, manifold, gaskets, vaccum hoses etc and listen for the revs to increase, you probably have a naff joint between two parts

Hi mate have you read the thread below that I created about my problem? Have a look and see if this applies, and its not as the titles leads u to believe

try removing the swirl pot from the front of the engine, put the pump feed stright to carb and blocking the fuel return. if that helps then you can try fitting a restrictor in the fuel return line after refitting the swirl pot, a welding tip is the recommendation I've seen.

this seems to be a common problem with the weber, not sure why this happens but my theory is there is a factory restriction on the swirl pot return which gets lost over the years but who knows