plenum off during install also. I ended up doing the EGR delete and replaced the heater core since I had the dash off. So looking down the back side of the engine at the firewall became much easier. I took the master cylinder off too, as I replaced that as well.
My car has been sitting and I have just been doing a lot of preventative maintenance and replacing things that are original. The o2 sensor on the drivers side was easy to get to with the harness out.