What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
The pilot states that while in cruise at 14,000' he mentioned to his wife, who was his passenger, that he wasn't feeling right. The wife mentioned that the carbon monoxide detector was indicating at a high level. They both put on oxygen masks and contacted sdl ATC to advise them of the situation. The aircraft landed at sdl without further incident. Maintenance at landmark aviation discovered cracks in the left muffler allowing exhaust gas into the heating system for the cabin.
As the FAA filed it
THE PILOT STATES THAT WHILE IN CRUISE AT 14,000' HE MENTIONED TO HIS WIFE, WHO WAS HIS PASSENGER, THAT HE WASN'T FEELING RIGHT. THE WIFE MENTIONED THAT THE CARBON MONOXIDE DETECTOR WAS INDICATING AT A HIGH LEVEL. THEY BOTH PUT ON OXYGEN MASKS AND CONTACTED SDL ATC TO ADVISE THEM OF THE SITUATION. THE AIRCRAFT LANDED AT SDL WITHOUT FURTHER INCIDENT. MAINTENANCE AT LANDMARK AVIATION DISCOVERED CRACKS IN THE LEFT MUFFLER ALLOWING EXHAUST GAS INTO THE HEATING SYSTEM FOR THE CABIN.