Yesterday's tune on a MY04 STi. Owner had recently bought the vehicle and booked it in to have the driveability problems fixed. On closer inspection, previous owner had removed the the Vi-pec ecu that was in it and put back the stock ecu. The front AFR and rear O2 sensors were also not present. (Vi-pec does not require the use of these sensors). Both AFR and O2 CELs were deliberately removed via a reflash to prevent the engine light from turning on.

In real terms, closed loop was not functioning at all.

Anyhow, both sensors were replaced and we proceeded with a tune.