Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I have a Toyota Hilux 2013 model, V6 4.0L (1GR-FE) engine with a free flow exhaust which means the catalytic converters are removed and the mini cat (LAMBDA Fooler) installed, all were working fine until couple of months ago i started smelling bad exhaust fumes almost like unburned fuel but no smoke at all.
I used (Nonda health monitor scan tool) it is very basic dongle but it has fuel trims i was able to check the vehicle and i saw that :
no matter the situation closed or open loop the % stays the same
STFT B1 = -95
LTFT B1 = 20
STFT B2 = 20
LTFT B2 = 20
I Also checked 5 other petrol (gasoline) cars with the same tool 4 of them also show -95 on the STFT B1 im not sure why..