Firstly, were these the plugs that the car was set up with? It is imperative that you stick with the same plugs if you have had a live map and pushed the car to the very edge. Changing the plugs for different heat rated ones is a big NO-NO once this has been done, as it changes everything.

If the answer is yes they are the same plugs, then if the car has been mapped on the road, it is IMPOSSIBLE to replicate the full load in fifth gear driving that some drivers then do on the road . The only way you can map for this is to go to Brunters or somewhere similar and max the car out and map for that. Even then that is not 100% safe . I shall explain: When mine was live mapped at Brunters (when it was 400bhp), I did three BACK TO BACK high speed runs to ensure that the fuelling / ignition was spot on. First run (to a Stack indicated 167mph - couldn't go any faster at the time, as it was absolutely pissing it down with rain and the bottom half of the runway had been closed off for some reason), no sign of det. Second run, similar speed and towards the end of the run, the faintest murmor of det appearing just before I shut off. Third run, and towards the end of the run, det could be heard (through Ahmed's cans). I was given a choice of backing off the ignition some more to make it ULTRA safe at the expense of losing some power, but knew I would never be able to hold it flat out for that length of time on the road and also that I wouldn't be stupid enough to do three or more back to back top speed runs in normal circumstances.

Obviously the point I am trying to make, is that if you don't INDUCE the conditions that make the car det, then you don't know exactly when you should be backing off the throttle. So mapping on the road is unlikely to give you this knowledge, so you can go away thinking that the car is perfectly safe, but as I have shown, after three flat out runs, det does become an issue. A fourth run without Ahmed riding gunshot to tell me to back off, may have seen the engine lunch itself.... On the road in certain conditions, you could have even held it flat for longer than at Brunters and that is when cars tend to let go, as the heat build up is IMMENSE. You really do need an EGT gauge, as it may have told you to come off the throttle.