CLASSIC MINI VACUUM PIPE END ANGLED 90 DEGREE 12B2062 AUSTIN CARB 998 1275 BJ16

The stock vacuum advance distributor is connected to the carb/manifold by a small rubber joint that in turn is mated to metal line that fits the distributor. If this little rubber connector is deteriorated it could allow a vacuum leak at the carb and stop the advance from working properly. The rubber connector has a 90 degree bend. When in doubt, replace it. 

Part number for reference: 12B2062