[slknv]

Was driving my 996 home when all of a sudden it misfired while driving, was able to restart and limp home. Have been in lockdown for ages so have done some wrenching, including:
PARTS REPLACED: Cyl 6 coil pack, spark plug & tube (first codes read was for misfire cylinder 6). Fuel pump and fuel pressure regulator. Alternator and starter. Crank position sensor. Oil pressure relief spring & piston upgraded.
PARTS CLEANED: Throttle body and plenum. IACV cleaned and checked with 9V battery. MAF cleaned.
PARTS CHECKED: Y cable checked. Battery holds good voltage. Swapped to another battery no change in problem.

No codes for misfire anymore.

From a cold start, car idles 100% fine at 1000rpm no issues. After 3 minutes, revs drop, motor shakes, eventually stalls. Restarting when warm then goes straight to bad idle and stalling. No codes.

Thinking something to do with change from open loop to closed loop operation after 3 minutes (but no codes for O2 sensors)?