Series 3 Series 3 running s@#t

Hi all, if the gasket between the two manifolds has blown would that make it Run bad.
It has new plugs with correct gap, points are good and correct gap too.
It had a new lift pump and aftermarket carb just before I bought it and ran fine until about three weeks ago.

I have ordered new gaskets to put on and if that doesn't work I am out of ideas.

When I bought it there was a box in the back and in it is the original lift pump and Webber carb. Is it worth having them overhauled and put them back on.
Been very busy with work so not had much time on it lately,. anyway thanks for reading and all idea's and suggestions welcome. Thanks, Simon.

ensure the 2 manifolds can move separately by loosening the 4 bolts clamping them together before securing both to the head, is spark good ,its a good idea to replace condenser ,rotor arm ,cap,leads coil ,points and plugs at the same time ,but bare in mind its very likely to find some poor new parts

See my thread on idling. Very similar symptoms. Not saying it's the carb but you are doing all the right things plus as James says. Weber refurb kits are £21.00 plus carriage. Workshop manual rates manifold problem as first thing to check.