After recent idling problems and replacing the MAF, split inlet pipe & Idle control valve the lambda sensor was not working but even after replacing this the problem has not gone away, it just seems everthing i do makes a small difference but is not the cure to the underlying problem.
I've now had to get the idle raised quite along to make the car driveable, partly due to the cams i have fitted and part due to the idle problem.
Just for reference the only way to adjust the idle is using Subaru's plug in diagnostics tool and it's special functions mode!!