yesterday i let my friend drive my evo 4, he drove it harder than i have ever done, im now getting the warning light come on.

this is whats happening:

When the engine is cold it starts up fine, but once it gets to normal running temp the engine warning light comes on, the engine still runs. I have no lose of power.
But once i turn the engine off and try to start it again the engine fires up and dies, the warning light stays on while firing up and stays on.

So i can drive it to work at the end of the shift is fine to drive but i cant drive it anywhere else ie popping to the shops......any ideas?

I'm looking over any simple things it could be before it has to be looked at.

checked oil level and topped up as it was on minimum. fault hasnt been cured
awaiting on new NGK iradium spark plugs

the other thing i have been told to try is lambda sensor. where will i find it and is there only one sensor on the EVO 4.

anyone post a link as to where i can buy one from?

thanks.