VESPA GTS Super 300 ie 2008 Service Station Manual page 204

Injection
Proceed with the injector seal test.
Dry the injector outlet with a blast of compressed
air. Activate the fuel pump. Wait for one minute,
making sure there are no leaks coming from the
injector. Slight oozing is normal.
Value limit = 1 drop per minute
INJEC - 204
Vespa GTS Super 300 ie (2008)