Engine cuts out at low revs after RAC start up

Hi all this is the red 1992 GTO auto N/A

Got in this morning having used two previous days with no probs and it would not fire but turned over fine. After few tries and no luck called out RAC.
They guy was older and seemed pretty knowledgeable and sat in foot to floor and turned it over for 2-3 minutes and eventually it stuttered for a minute then burst into life.
He said damp weather and todays fuel meant it did not fire initially and confused the computer which basically kept priming with fuel and had flooded it, so by keeping foot flat on floor this meant air was going in not fuel.
Took it for a 20 mile motorway blast as he suggested and all fine albeit it did fluff a bit at 90 so came back to 70.
However coming back into town it stalled at lights so had to restart or keep revs to 1000 or so with foot on brake.
Winter is here so the weather conditions for last 5 years have never caused anything like this!
Any suggestions what else it might be?

Could it have been a bad batch of fuel ?
Have you tried putting fresh fuel in it.

I am tempted to believe the RAC guy about the overnight atmosphere now as left it sunday parked up and yesterday and today it,s cleared and starts, runs and idles perfectly. Had and still has half a tank of fuel so probably not that.
typical 30 year old temperamental Japanese beastie.

No cost for repair so brilliant. Off for it’s touch up respray next month. Wing mirrors
black crescent on boot gate and chip on aerofoil and parking dent.