What you will need:
Soldering iron (example: https://www.amazon.com/Liouhoum-Auto-Sleep-Adjustable-Temperature-Thermostatic/dp/B08PZBPXLZ -but- any reasonable pencil-type iron will work fine)
Recommended option: Heat-set adapters to fit that soldering iron (example: Leo Sales Ltd. Heat Set Insert Kit (M3: M4: M5) – Micro Center
A small bag of heat-set inserts (example: Leo Sales Ltd. M5 Threaded Insert Knurled Brass Nuts – Micro Center, you’ll need 14)
At least seven (7) M5 x 20mm cap screws. (optional – washers that fit the screws; cap screws with button heads instead of bar, Torx(R) instead of hex – see instructions)
A (preferably electric) drill and two (2) drill bits, one just bigger than the threaded part on the M5 screws (call it A) and the other just big enough to make a hole that admits the necked down narrow end of the heat-set insert that you’re using (call it B).
A chassis reamer (example: https://www.amazon.com/LifCratms-Tapered-Chamfer-Reaming-Woodworker/dp/B0BXG6QZKB, can be used instead of the drill for the heat-set inserts)
A couple hours, tops.
Optional: new seal strip, bushing and mount cushion for the air box (example: items #4,5,6 here: https://www.tascaparts.com/v-2009-volvo-s80–v8–4-4l-v8-gas/engine–air-intake)
Instructions
1) Remove the airbox from the car (detach the air horn that connects the airbox to the throttle body, and swing it aside; unplug the electric cord from the MAF (you can leave the MAF right where it is); lift box from engine bay then clean and dry it (soap & water, Windex, Fantastik, Zif, ?).
2) Using drill A enlarge the screw holes in the airbox lid. Be sure to drill STRAIGHT in or else the screws won’t hit the box bottom correctly.
3) Using chassis reamer, working from underside of air box lid clean the drilling frass from around the now enlarged holes.
4) Working from topside air box lid, insert a cap screw into a drilled/reamed hole; working from underside of air box lid screw on (but DO NOT cement, stake or secure) a heat set insert such that it “hides” in the opening under the respective hole in the box lid.
5) Repeat (4) for the remaining screw holes.
6) using drill B chase/clean out the screw holes in the air box bottom.
7) using the chassis reamer,
6) Attach the (recommended optional) heat-set adapter to the soldering iron, or use a CLEAN conical tip that fits your heat-set inserts (works but not recommended), turn on the soldering iron and if adjustable set it for 250 deg. C (if not adjustable don’t worry about it too much).
Explanation for (6): It is mad easier to get the heat set inserts in straight using the heat-set adapters rather than a soldering iron tip. If your soldering iron tip is not clean, you likely will have problems with slag or solder in the heat set threads. A heat set adapter is cheap and will speed up and improve quality of the heat-set installation. The temperature setting is helpful because it can keep you from burning the heat set hole too big, however, in practice that’s a manageable problem. You see, when heat-setting an insert, the slower you go the more durable the heat-set insertion is. if your soldering iron is NOT temperature controlled then for say a 30W iron the working temperature will be 380 – 400 deg. C – a bit hotter than you
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