Working on a Lennox 10GCS042 with LP, customer complained about an odd smell. Unit is sooting up the exhaust really bad and has a stink to it while running. Checked a few things out and I have 11.8 gas pressure coming in, 9.6 out, adjusted it down to 3.5 and it starts lighting in the burner tubes. Orifice size is 54 just as Lennox supplies in the conversion kit, spring in the gas valve has been changed as well so I don't see it as a conversion problem. There is not a gas leak (not that kind of smell to it) and the heat exchanger does not have any holes in it, any idea what is going on?