ahaa...

Ais pipe wasn't on properly.
Don't think when I blocked it originally that I'd put the hose back on and that it was just hanging on the edge, including the spring clip and must have just come off over time.

Had another thought Kev, didn't you say that I'm the only person you know who has got a PCV AND an Autotune?

I only wonder because technically, if when the O2 sensor is disconnected and normal eliminator is applied, the ECU changes the AFR between lean and rich at points below 20% throttle between 2500 and 6000 rpm.

Well, technically, if the ECU is doing that, and the autotune is switched on and monitoring the AFR in real time, and making trim changes in real time and applying them whilst your riding, surely the Autotune will counteract that?

So, as the ECU changes to rich, the autotune will lean it out because it'll see the AFR change in real time.

Granted, the map will be very, very messy because of it being all over the show, however, the autotune should do its job and keep the AFR at a constant when riding so no actual surging will be shown by the bike despite the ECU change.

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09 XT660X:

CCC Stainless Rounds, Stage 1 DNA, Stage 2 DNA, PCV With Custom Autotune Map, PCV AutoTune, Home made O2 eliminator, Self machined Fork Spacers, DIY Autotune Switch.