Driving through the wet is the best way I can describe what I can hear. It sounds like the sound of tyres on a wet surface.
There's no backfiring and it idles fine.
I did a long motorway drive recently and around an hour into driving the car lost acceleration on a very very slight incline, it then really struggled with uphill for the rest of the journey. This was a couple of weeks ago, and I put it down to the car being fully loaded with the whole family...