So...my 85 340 1.4 randomly ran like crap one day and cut out. It was backfiring from the carb and was somewhat driveable but the revs had to be kept high and couldn't idle. Got it back to my driveway to investigate and changed dizzy cap, rotor arm, HT leads were already pretty new, checked the Renix unit, changed the gaskets on the carb (Weber 32 DIR 109), idle control valve all okay. All through this it would just backfire through the carb and didn't have power to make it up slight inclines.

When turning it on now, it seems to idle really high and does backfire under hard acceleration. It can idle without the choke eventually, but it's really sensitive and will immediately cut out if you even put the choke in slightly before it's ready.

I took it to a garage and they said the choke diaphragm has collapsed and that the carb is worn, but the car is only on 51k. They also said it'll need head work as one of the valves on cylinder three has started burning up, which is causing it to backfire through the carb every now and then.

Not sure what my next step should be. Do I get a choke diaphragm or just buy a refurbished carb?