Lumpy weber

Hi. I have a Weber 36 TLP on a 1.5 auto that's now rough at idle. It ran beautifully on the old engine for 5 years but since I've put a new engine in I can't get it to idle well. It's particularly unpleasant in drive when stationary, the car shakes. It has a complete new ignition system: Powerspark, New coil, plugs and leads and dizzy cap. New fuel pump. All new fuel lines (before the engine change) .  Ignition timing has been checked. Valve clearances checked. Gearbox serviced. Carb rebuild kit done. I'm running out of ideas. It runs very nicely and smoothly when you're moving and it's doing 30 mpg +, the problem only occurs when you stop!
Could it be the fuel separator or filter? It also runs better with a tiny bit of choke which makes me think of fuel but don't kow where to look next. Any ideas please?

did you change the flange between the inlet and the weber/adaptor? also i dont know if its like the later cars but on those there is a steady bracket between the head and airbox which stops the carb flapping about so much, without this the flange above can split

Yes I changed the gasket. It's only a normal gasket on this one. I've also changed the inlet manifold gasket. it almost feels like a slight air leak or fuel blockage at low revs as a tiny little bit of choke has it running much more smoothly

righto, try running the fuel pump direct to the carb, remove the swirl pot and cap the fuel return. some have found this is the only way to keep the weber happy. if it does help then you can put a restrictor on the fuel return, a recent thread suggested inserting a welding tip in the fuel return pipe

Thanks. I'll give it a go over the weekend. Cheers

Fuel fix tried. Not much difference but…. discovered it has a 1.6 head on ( I bought it already built)  so as suggested I've refitted the 1.5 cam from the old engine and it's immediately smoother. Just needs retiming and tuning up now.
Thanks for all the help, it was all very useful info.
Cheers. John