Had similar problem on my Focus RS a couple of months ago, a mate put his diagnostics kit on it and the error code led us to 2 main possibilities, pre-cat lambda sensor or split hose. Because it was still driving fine we first changed the sensor but within a few miles the engine light came on again and the driving became more erratic with the idle becoming more and more lumpy, then i could hear a hissing noise when it was ticking over on my drive and i managed to trace the hose that had a large split in it causing the hose to collapse on itself. We changed the hose and it's been fine since so i would check your hoses to see if any have split.
TBH i know bugger all about Octavia VRS engines but i presume the basics are the same so you never know, it could be a similar problem as i had.