2001 Volvo S60 non-Turbo with 153k miles.

Did an oil change, coolant flush, and MAF and ETM cleaning this weekend. Engine sputters and stalls while in Idle and only when the engine gets hot (all fluids are topped off).

Here's exactly when and how it happened:
Car was slightly jacked on the passenger side
First flush: With a warm engine, we drained coolant and filled with a 'flush' and water and ran engine for 10 minutes and drained fluid. We ensured radiator was topped off.

Second flush: After draining, we filled again with just water and ran the engine for about 10 minutes ensuring that fluid was always topped off. As I was about to turn off the engine, it sputtered and died. We completed the flush and refilled with coolant and jacked the car back down.

Car idles for only about 30 seconds before stalling. No "Check Engine" light or DTC Codes were available. Fuel vent system, oil separator tube, and fuel relays are okay. Car only dies when engine is idling, it will not die when I have my foot on the gas. Retested this morning while engine was cold, car idled fine for about 1 hour then stalled again.

Could this be related to engine temp sensor or fuel pressure? We are waiting on a fuel pressure gauge to come in so that we can test the pressure. It's just weird that it seemed to happen during the coolant flush and not sure if it's related or just pure coincidence. Car was running perfectly fine before hand. Thanks in advance for any feedback or help.