Guy: I spliced into the can wires at the obd (under the dash).
if I remember correctly, sorry it's been a few years, the Maestro instructions told me which wires I needed to tap into so I cross referenced the RX-8 wiring diagram and that did the trick.

 

Okay, it makes more sense now that I checked the back of the obd port.

So I just stick those two wires into the same two holes (6 and 14) that already have wires? Will they both fit in there together at the same time?!

And then on the 7510 harness, I need to splice more cables in and make some 3-way connections.

I didn't receive either one of those cables that I need to splice in. I only received the one black wire that plugs into the head unit and maestro. So I just went ahead and finished installing just the new head unit and metra kit for now, and everything appears to be working as it should, including the A/C. It will probably take a week to sort out the issue with the missing cables from the ebay seller.

 

You can use wire tap clips like this to tap into the OBD wires, don't try to jam more things into the connector. I did the same thing for my GoodBox.

 

Don't try to jam two things into one hole...wait, that came out wrong.
Listen to Loki, that is the way

 

Ookay, nice. Thanks.

Should cruise control still work after all this? or is that sacrificed?

 

if your cruise control stops working, you've done something terribly wrong.
all OE functions remain operational

 

Okay cool. I took it for a drive today and cruise control does work fine. I just tested everything on battery last night, not an actual drive.