Gas smell when starting heil furnace

I have been experiencing a odor that maybe gas coming from my heil furnace whenever I start up. I have changed the gas valve but not the manifold or orifices. I have changed the filters, and cleaned the exhaust vents. The gas supplier came out to inspect the system and found what they say is gas leaking at the orifices this is the reason I changed the gas valve. But still getting the same with the new gas valve. So what are the possibilities that the new valve is faulty like the old. Could the gas pressure coming from the valve be to high causing excessive gas to linger after the system has shut off? Could the board be malfunctioning causing the valve to not close completely. When the system starts I get the fumes strong when it shuts down them fumes disappear until system kicks back in then strong fumes immediately. This is causing me to experience headaches, nausea, sore throat. System seems to be heating but not that great. Any help would be appreciated