clio 1.2 16V non runner 54 reg,please help?

I have been a mechanic for 25 years and am puzzled by a Clio 1.2 16V 54 reg,the problem I have is I picked the car up at auction and it drove perfectly but was low on fuel I drove it 2 miles and put £10 worth of petrol in it and it still drove fine for about 10 miles and then it started to get a flat spot on acceleration and then when i got to traffic lights it started to race away to 2000 to 3000 rpm I then managed to drive it another half a mile and
when I got to the next set of lights it just conked out so I pushed it to the side of the road and after a couple of minutes it eventually started with an eggy smell but was racing away at 2000 rpm,I managed to coax it home and put my computer diagnostics on it and it said NO CODES STORED, I was of thinking maybe it was the cat but then this would not make it race away at 2000 rpm,so I then took off the throttle body which merely exposed the butterfly valve but cleaned it anyway.I the had a heck of a job to get it restarted but eventually away it went, I took it for a short drive and it conked out again,back at the garage I then took out all the relays and fuses by the battery and cleaned them up as they suffer from poor connexions even tho they all seemed to be ok,I am still unable to start ther car and it seems to be flooding,I tried easystart and it fires momentarily but still wont go with or without easystart,Have had the plugs out which are very good ,have a great spark,have good fuel to the rail but no joy.Was wondering if poss throttle body or ECU was faulty but not sure as no code on the diagnostics.Would really appreciate any advice/tips to a fellow mechanic.Forgot to mention it used the £10 worth of petrol for about 20 miles of driving and I have since put in another £10 in case the fuel I origionally put in was duff.