When you convert from natural gas to LP or back the orifices should be changed as you did but the spring in the regulator or the regulator pressure should also be changes. LP has approximately 2 1/2 times the BTU’s per cubic foot as natural gas hence the much small orifices for LP compared to natural gas. If the regulator or gas valve are made to be converted the manufacturer can supply parts and instructions for the conversion. Sometimes it’s just a matter of inverting the plunger but you would have to check with the manufacturer to confirm what is needed to convert. Normally pilots have a different orifice when they are converted also. If the pilot orifice hasn’t been changed you are producing much more heat than it would have with natural gas.