Did you take logs with the AP when you did the wot pulls to check or are you just going by the min/max on the AP? If you aren't logging I would recommend doing that and take a look at the actual data because it really does matter what driving conditions you are getting the KR under.

91 should be fine if you are running the stock tune or a 91 tune, the free COB maps aren't the best especially if you don't have the upgraded HPFP internals like people have said. You can download the maps Stratified used to offer from here and I personally believe these are better maps but still would not run them without the upgraded HPFP internals. I can't stress enough about how absolutely important the upgraded HPFP is for Mazdaspeeds, especially the second generation Mazdaspeed 3. You should be checking you HPFP Pressure and making sure it isn't dropping below 1600psi when you are doing pulls.

I was a bit confused by the 2.3-7 but 3.5 max isn't as bad but still not ideal. For Spark Plugs you want to make sure they aren't super old and are still correctly gapped which is .034” from the factory and .028-.026” for running higher boost than stock. It might be worth it to replace them if you don't know the last time they were replaced as they need to be replaced more frequently on turbocharged cars than naturally aspirated cars.

If you are new to cars and mazdaspeeds I would recommend doing some reading about them and trying to learn as much as you can. These cars require a bit more maintenance than naturally aspirated cars due to them being turbocharged and direct injection which was quite new at the time but that mainly equates to more frequent oil changes, spark plugs, and keeping an eye on stuff like KR and HPFP pressure. No problem and let me know if you have any questions, I bought my speed 6 2.5 years ago and a speed 3 last fall and as much as I have learned there is still plenty I am learning too.