Wonder if someone could shed some light on my issue....

I have a 06 WRX, yesterday, nice long run from MK to Chester Racecourse and back again, no problems at all, this morning, just driven down the road about 5 mins and the Engine Management light came on, car running perfect as always, I've had a mate come round tonight with his ECU data monitor reader thing, plugged it in, no fault code have come up, no previous fault codes have come up, he's resent my ECU, the light has gone off, however when you rev the car slightly, it comes back on again. Also when my cooling fans kick in, you have a strong smell of exhaust gases coming from under the bonnet passenger side.....

Any one any ideas?

 

mates reader not working perhaps.. as if light is on then there should be a code recorded