E30 Zone

Need some help, mate has a 1998 e36 318Ti which runs perfect until its hot and which point it splutters/is down on power and backfires. Also seems to smell like its running rich. Tested the blue temp sensor both at the ecu then at the sensor itself just to be doubly sure. Was exactly what it should have been.

So any advice where to be looking next/what to test?

Just take off you air flow sencer and take it for a spin it happened to mine it worked after that so got a new sencer

If that's not it tho I don't know :/