I think what you are seeing is your muffler leaking condensation from a weep hole. This normal and will stop after your vehicle has reached full operating temperature.
Doesn't have to be anything wrong. Some condensation is a natural result of the combustion process.
carbon monoxide
No heavy water in the muffler.
"Wrong" implies that there is a standard. It is rare that a condominium community would define a "right" detergent for use in its facility. Classically, detergent does not cause plumbing leaks.
heator core
You have described the classic symptoms of a blown head gasket or cracked cylinder head or both. In either case, there is a loss compression and "get up and go". Also, coolant leaks into the combustion chamber (also affects "get up and go" and the steam comes out of the muffler/tail pipe as "white" smoke.
If there is a rotted hole in the muffler please replace the muffler. However, if there is a small hole at the bottom end of the muffler it is there to allow water to escape.
Oil comes up through the head (top part of the motor) and leaks from the muffler.
No, Do not drill a hole in your muffler! The water evaporate when the car gets warmed up. If you drill a hole in your muffler, The next time it gets inspected it will fail.
If that's going on you might want to check for vacuum leaks and make sure the engine isn't running lean.
The radiator may be plugged. Take it to a radiator shop.
By installing a new mufler you have changed how the car runs.If the wrong muffler was installed it could mess up the computer until it would not run any moreorThere is a problem with the new muffler or how it is installled.