Running Problem - Help Reqired

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
tank checked - clean
Bypassed swirl pot
Tried restrictor in return fuel line
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 anythingDocc       

Are you sure the carb is correctly jetted for youR engine?
Sounds either like fuel starvation or over fueling -does it smell strongly of fuel ?

Have you tryed the gasket under the carb

It doesn't give a strong smell of fuel and the carb was a brand new replacement together with a new gasket as well so all ok on those fronts

Spluttered when 1st started this morning then ran ok but scared to go over 2-2.5 revs and was on half choke for approx 8 miles

Are you using the standard air box and does it have a hot air feed pipe from the exhaust manifold fitted?
Went the car is ticking over try wobbling the carb on it's mount to see if the engine tick over changes.

1/2 choke for 8 miles is not right, do you know what they set the carb on the emitions when it was tuned?
The webber is a simple carb to set up but it only takes a tiny amount of movement on the mixture screw to make it to rich or weak.
As already said is the carb set up for for size engine as webbers have different jets to differnet size engines.

hi mark1gls, yes the car i mostly standard including the air box with the hot air feed pipe fitted although the duct pipe is really perished and a new one is ordered, pick it up tomorrow do you think that could be the cause?
the tuner guy said it was running lean which was the opposite to what i thought it would have been and the carb was a direct replacement for the 1.8 from Southern Carbs and i was told it was ready for immediate fit out of the box

Does sound like fuel starvation, especially as you say adding choke makes it better. It will have an accelerator pump jet which adds more fuel under acceleration, hence why you manage to get it to rev higher.
Have you set the mixture on a co meter ?
Does the float chamber remain full of fuel ? Or is your engine using it faster than your pump can supply it ?
Do you have any air leaks, carb cleaner is quite good to spray, listen for revs rising if there is a leak.

I had assumed that the tuner guy would have covered all of those items so will re-visit him and ask the questions.
I'll check the float chamber tonight however i did bypass the separator direct to the carb but issue still ocurred and new fuel pump fitted. I read an old article about elongating the pump mounting holes to create more lift due to possible cam wear?
Ive sprayed and couldn't notice any changes in revs

Cab is now in the workshop being looked at by a old school guy who came recommended. Will keep all updated