Help please! I changed spark plug by myself as a part of annual service. But firstly the shopman gave me a wrong set of sparkplugs. That was terribleÂÂÂ

I asked them to give me a change of right set. Then a problem came out.ÂÂÂ

The engine cut out when I stopped in front of traffic light or approached to a roundabout. I changed fuel filter, air filter, cleaned carb and changed idle speed. Doesn't work! Could you please give me some suggestion? My car is Golf MKII, Carb, 1.3 L and was a really nice one. Many thanks in advance!!!!!!