If the cats ok and if you have too much fuel and a leak in the exhaust near the rear then its a good combination for a flame, although exhaust is on pressure, sometimes pulses allow air to be sucked into exhaust from holes after the muffler,

the fact that it burnt long enough to catch upto you sounds like it was burning slower than petrol would???

did it look like those flames that come from the sides of v8 supercars?

It looked like fire man, I wasn't too concerned with seeing exactly what it looked like at that point in time Mike my exhaust is good, it's only about a year old so no holes in it. Some original photos have not been recovered yet.

maybe ur car just cant wait till it runs 10z n is getting a bit excited

someone could sprayed a can of crc into the exhaust Some original photos have not been recovered yet.

it can only obviously be soimething combustable so fuel or oil is your answer but why?

^^^ Indeed, I'm going to go with oil rather than fuel. There's oil through the intake and through the turbo, not heaps but more than I would expect. The fact that the flame got past the cat and muffler is pretty odd though. It's not much of a muffler, and the cat is a 3" highflow, but still... if I can see the flame out the rear window it's pretty massive.