Wonder if anyone could point me in the right direction for this one?
The last 2 days my 80 has a fuel smell inside when driving (cabin vents), seems to be more intense when cold or racing the engine... I have had a butchers under the bonnet to no avail

No obvious leaks, but have noticed a slight back fire (pop pop) when gearing down from the exhaust.
Suggestions to the cause/fix would be greatly appreciated.
Chrisp.