Just replaced our 14 year old heater with exact but new Maxi Therm 333LP. Heater lights perfectly, but burner sounds a bit muffled and it seems the water coming out is not near as warm as old one (before core went south). Reading the troubleshooting ,it says to check gas pressure or replace orifice. I try to do everything myself and have a mechanical background. any suggestions? Cant see why regulators would need to be different with same model. Thanks in advance!