RarisRX-8

So as my RX-8 is down for a few weeks (waiting to get mazdaedit and get it tuned, tires, clutch, brake pads, cat, and inspection) i figure i overhaul it to the best of my abilities.

I have a P0420 cat eff. below threshold (i know the cat is bad; will be replaced before getting tuned)

thus far, i have done the following...
cleaned MAF sensor
cleaned intake
cleaned TB
all new oil/coolant/clutch and brake fluid/plugs/coil packs/plug wires/trans fluid/rear gear oil
inspected/checked all suspension, brakes, wires, hoses, connections/grounds, lubed everything, and cleaned it meticulously as well as lubed all electrical contacts.

i want to totally clean the UIM and LIM as well as SSV and ESS. i have searched, and believe this is a fairly comprehensive list. Shes got 131k miles, original engine, excellent compression, i removed/bypassed the VFAD system and it also had an aftermarket exhaust which has melted the exhaust shrouds lol. I am on the fence in regards to cleaning the motor with distilled water via service ports...

I have a few weeks off, every tool i ever needed to tear down, build and rebuild a honda/acura, cherry picker, etc, and was wondering if there is anything else in particular i should check for/clean/service while im at it.

its running fairly rich and backfiring a lot, so not driving it till everything is resolved. Besides, i have my dads TRD supercharged Tacoma to drive in the mean time

any suggestions are more than welcome!