Volvo V40 2.0LPT 2001

[bobe84]

Recently i got P0139, i deleted after ~200km it came back, so i will be probably inspecting my rear O2 sensor.
What is bothering me, is exhaust smell when i accelerate hard in 2-nd 3-rd gear, not huge smell but traces that are noticable.
I read somewhere that PCV system can cause this, so i pulled dipstick, and it has small vakum on it.
I have small exhaust leak in the back of the vehicle(the small thing before the last exhaust drum).

My question is where the smell is comming from, how to locate it.
P0139 means that O2 sensor behind the catalysator had slow response on changing a/f mixture.
Anybody with some useful advices are welcome.