Do I have a gas valve leak?

Unless your boiler and other gas appliance have been checked with a manometer or other gas safety checking device you are unlikely to have any reassurance as to the soundness of your system.
It is also illegal (and a very serious offence) for an unregistered plumber/gas engineer (home owner or otherwise) to tamper with gas fittings. For yours and your neighbours sake I would recommend you call a registered gas engineer to check your appliance as soon as possible.

Red hot
December 2010