OK to just unplug aircon pump, no errors caused just aircon won't work.
On the 185, the 7 stud manifold normally warps and this is normally associated with an exhaust leak and pulled threads in head - may be people overtightening to try to cure leak or could be manifold warp was enough. Either way, helicoils are IMO the best answer. You can get 'repair studs' with a larger thread one side, these are a pain to get out in the future when the nut has stuck itself to the stud, which then can't come out through the manifold.
In your case, if you have an XS power manifold, these have a habit of not being flat from the factory so a skim may be in order (or get a standard one)
Turbo nuts do sometimes come loose, usual solution if they keep coming undone is to buy new ones from Toyota - not cheap but they are very special and don't come loose.
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If at first you don't suck seed, try drier grain.