Are you 100% certain they o2 sensors aren't the wrong way around? I took it to 2 workshops. One did the work on my car and they said it's not possible to put them the wrong way around and denied this possibility. The other workshop said they were the wrong way around. I've already payed to have 2 new o2 sensors put in. It's a pretty big job to change them around so have not looked into doing that yet.
I had a DP fix a while ago and since removed it, and I'm still having this issue.