I enlarged the O2 system hole to 2". I had to offset it a bit toward the drivers side too.
The Haltech R3 provides substantially more functions than I'll need but I don't need a fuse box so maybe it was worth the extra $1000 OUCH!! There's a ton of wires.
The lump under the carpet will be a lot bigger now than with the old O2 wire bundle.
Here the ECU laying on the metal plate I attached to the old O2 mounts. Time to take it off, drill the holes for the ECU and paint it. Reading through Showdown's excellent thread, that extra real estate may come in handy someday.
https://forums.pelicanparts.com/porsche-911-technical-forum/1106768-when-well-enough-cant-left-alone-backdate-efi-itb-ac-more.html
