1994 Hyundai Pony Melting Vacuum Hose

Hi there. I've got a '94 hyundai pony 1.3(?) chintz thats done 64000m. There is what i think is a vacuum diaphram that is connected to the inlet manifold by a 1-2 inch length of rubber pipe and has two small diameter pipes that dissapear somewhere around the carb. The problem is that the main hose keeps melting and bursting , new ones burst in about 2 mins and a new diaphram unit makes no difference . The problem seems to be alot of quite high pressure and very hot air blowing from the inlet manifold into the diaphram and yet it does not look like it is supposed to be anywhere near anything hot. I would appreciate any help or advice with this . Thanks.