I had a similar "failure" about 2 years ago on my Gtv, check the pipe from the n/s of the rack that run's up behind the header tank and the airbox mounting bracket.
It can chafe around that area and its just a small length of rubber pipie, i replaced mine with a length of petrol hose and has been fine.
It's the cheapest fix iv'e had consdering i thought i was up for a rack or a pump.
Another thought it could be a collapsed pipe that's stopped the resevoir from comletely emptying and it's burst lower down.
Every time i see an Alfa Romeo, i raise my hat.
Whenever i see the front of a Gtv i become sexually aroused.