When I had my car road tuned, it was running lean no matter what my tuner did with the maps. We really thought it had to be the fuel pump.
Took it to dyno, had fuel pressure gauge hooked up and its running nice and sweet, ideal fuel pressure 43psi I think, no lean issues. Had it tuned on dyno nice and well.
Took it once more to the road to check AFRs and that everythings ok. Car runs really amazing after the tune but... guess what, afrs were screwed again, running lean on the road. The wideband sensor was straight off the tailpipe.
Back to workshop, scratching heads, then the workshop owner suggested to use his bung - basically now we connected the wideband to a roughly 20cm long metal tube and clipped the whole thing back in the tailpipe - dont ask me how, I dont remember lol..
Out on the road again and....absolutely brilliant AFRs (no leaning whatsoever) - as witnessed on the dyno during tuning...We are like WTF? That little metal tube made a huge difference to the sensor's readings. I think it was because of my XForce oval exhaust which has a
perforated metal tip and insides where the sensor was mounted - this possibly messed with the exhaust flow / turbulence and increased the air supply (outside air??) into the sensor, hence lean out issues.
The pipe possible solved that as it was not perforated like my exhaust tip and walls inside.
But yeah, this was definitely an issue that my tuner never had with any car before...
Lesson learned - Use a pipe in your exhaust and put your wideband in it. Or better still, make a bung in your dump for the wideband which is what he recommended.