986 Engine cuts out

[Alan2b]

Hi. A new member here.
I seem to have a very similar problem.
Engine suddenly cuts out with no warning and no CEL or error codes.
Took it to Porsche and they said it was cats had failed due to ignition coil packs which were failing and causing missfires (burning out cats due to unburnt fuel getting into them).
Changed coil packs, cats & lambda sensors & thought problem had gone (200miles + driven without problem) but happened again at weekend.
Initially after it dies, it will just crank over and refuse to fire.
After waiting a bit longer (about 10mins) it fires and goes into fast idle - but after a few seconds revs start to drop (to normal idle) and at this point it pops & bangs and cuts out. At this point giving it a bit of boot you can keep it going for a bit, but just more backfires etc and eventually dies.
I had been thinking it could have been heat related but last time it happened almost immediately (the car being started from almost cold - having been stopped just a couple of hours before - after 60miles without problem).
Dodgy relay sound a possibilty - burnt contacts??
Did you get to the bottom of the fault & which relay was getting hot?
Any help / suggestions would be appreciated.