If it were my car, I'd just replace the CMP sensor to start with rather than try re-wiring as I've seen those sensors go bad. I've also seen bad trans speed sensors too on older 850s.
As for the lower air box, they just pull upwards from the outer side (closest to engine) as they're held in by two plastic clips on the bottom, then it pulls away from the fender side, nothing to it. There's a sensor on NA cars with two vacuum lines and one plug that needs to be unplugged and on the turbo cars, there's a sensor that needs to be unscrewed from the lower airbox (2 #25 torx screws, easier than trying to unplug the vacuum hoses in that case).