Hi can anyone give me some advice as have had gas board out to problem posted last week boiler will ignite only with the flue off when you put flue back on 90 dg bend boiler goes into lockout if you take flue of bend boiler will ignite bas board been put a new air pressur switch on thought he had solved the problem but not so he took flue out boiler ignited he said he does not know what wrong will bring someother technician out , think just going to match any ideas whats going on Tahanks Bri