Lambda fault

Hi guys. After doing an oil and filter change this weekend I noticed that my vRS was running a little lumpier than before and it also seemed down on power, almost like I was towing something. My first thought was that the timing had jumped but there was no noise when I started the car up and it idles fine. I took it out for a drive and let it warm up like normal and don't think I took it over 3500rpm. No engine management light on at this point.

Once warmed up, I gave the throttle a prod and it was definitely down on power and also, the power delivery wasn't as smooth as it should be. Strange thing is, when the revs go over 6000rpm, it pulls fine. I backed off and drove gently home and after a few minutes the ecu light came on. Got the car on vcds when got home and I got a whole host of misfire faults as well as two lambda faults. I cleared them all and went out for a drive again. Within a few hundred yards the ecu light was back on and after scanning it again, just the two lambda faults had returned.

7670 lambda sensor B1 S1 Malfunction in circuit

7682 lambda sensor B1 S1 Negative lead open circuit.

Would a lambda fault cause my car to run like it does? And does this look like the pre cat or post cat lambda sensor? I suspect it's the first but you never know!