IDLEING ISSUES...I THINK!!

Can anyone shed some light on my issue….I have a 1800 golf cabriolet, i have just had a webber carb fitted and the engine ran lovely….i took a trip out init and after about 2 hours the engine strarted to chug and lose power when i turned the engine off and left for a few minutes it would start again and get me a few more miles, after this trip the car runs badly always cutting out when coming to a stop, and the engine when in idle chugs and shakes like mad …please help
Thankyou Jason

new carburettor. wonder where the problem may lie?

something has slipped or not been tightened down correctly, spray some wd40 round the base of the carb with engine running see if it revs more. then use a colour tune to check mixture (or a gas analysier if you have access to one)

carb icing problems? check the warm air flap in airbox opens and the pipe from airtbox to metal shroud is intact