Thanks to @
F1point4 for his excellent Borla UEL header installation DIY. The OFH install was quite similar with only a few differences I'll point out.
-Put the car on a lift (if you have access to one - it will make the job way easier)
-Remove the skid plate
-Remove the fiberglass splash pad
-Unclip the two O2 sensor wire harnesses and clips that keep the wires secure
-PB Blast the old exhaust manifold to engine block nuts, the nuts on the bolts connecting the old exhaust to overpipe, the front pipe hanger bolt, (if replacing the overpipe, also PB Blast the over pipe shield bolts and the overpipe to front pipe nuts)
-After giving the PB Blaster a few minutes to work, loosen the nuts/bolts just sprayed
-Note:
If one of the exhaust manifold studs loosens instead of the nut, don't fret and just remove it as is without changing the nut position on the stud. If the nut didn't move during removal, when you re-install it (torqued correctly) it should hold just fine. If the nut did loosen, but the stud removed, re-tighten the nut at least as much as the other nuts were while torqued and then reinstall.
All pictures are oriented with the front of the car up.