I think its funny you are willing to build plug wires again
With the "fixes" you will hopefully be back at 194whp (I think thats right) although that busted cat may explain another reason you were down on the power last pull...
Going to larger 3" exhuast I'd expect to see you right at 198-200. That engine is still fresh and with the better exhaust it should make a few more.. that last RX8 made 198 or so up there with similar mods and weaker exhaust.
Side note... if I can get all these repairs done to the 8 in time, I'll jump up there about the time you're done with the new exhaust. I'd like to redyno and see if my engine is still healthy like before, lol. If it is, you'll be duplicating that 3" exhaust.
You putting any resonators in?