If it stops next time undo the fuel pipe attached to the fuel filter at the tank end and blow down the fuel line you should hear bubbles from the tank. Try and restart the car and if it starts and runs ok you may have rust etc in the fuel tank and a blacked fuel pick up.
Could also be a split carb flange, do you have a standard air box and a bracket holding the front of the airbox to the rocker cover?
Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323