As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN APU BLEED AIR VALVE SWITCH IS TURNED ON HOT NOXIOUS AIR RUMBLES INTO CABIN AT AN OVER COMPENSATING RATE. REMOVED LEAKING PAX ACM AND INSTALLED AN OVERHAULED UNIT, REMOVED 2 COALESCER SOCKS AND INSTALLED 2 NEW SOCKS. LEAK CHECK GOOD, ALL WORK PERFORMED IAW CE650 MM CHAPTER 21-50-01.