Did you replace your front O2 sensor yet?

That code is "front O2 sensor slow" so that means that it's electrically, internally not responding as fast as required. Cleaning it is a waste of time as they don't clog. I've never heard of that before, nor would I ever advise trying it.

I also would never buy an aftermarket O2 sensor for a Volvo but that's my opinion and I have no experience with aftermarket O2 sensors. I'd replace it with OEM and be done with it.

I also doubt that "fuel qualaity" is an issue unless you're running very cheap gas with impurities or lower octane than expected. I try to use better quality fuels like Amoco or Mobil (93 octane premium only) in my turbo Volvo UNLESS prices skyrocket and I'm looking for a bargain (rare) BUT fuel quality won't effect the speed that the O2 sensor's responding, you need another O2 sensor for THAT code.