Many might notice that if you drive along gravel or sand with windows and/or sunroof cracked at about 45km+ the cabin sucks in a lot of dust and exhaust fumes... I experienced this in two MUs already.
You need:
1. Isuzu Mu
2. Well ventilated area
3. Up to 3 filler foam cans (longer nozzle and upside down working cans are your preferences)
4. Long sleeve shirt, gloves & goggles (that stuff is toxic)
5. Rags
6. Trim Clip removal tool or a flat head screw driver.
Preliminary
All this smog gets in through the gaps in lower rear quarter panels. There could be many ways to block those. I used Builder's cavity expandable foam (aka "space invader foam"). Sikka is a good brand and three bottles were more then enough. At $12 per can at Bunnings it's a bang for your buck. I would recommend fire proof foam for obvious reasons. And search for a can that can work upside down as well as upright for ease of application. Longer nozzle also helps.
1. Access.
To get to the cavities you need to remove inner trims. Left hand side is fairly easy. You can do the hole job via a latch for access to your tools and bottle jack. Remove those for ease of access. For the right hand side you need a clip removal tool or a flat head screw driver will also do. Carefully remove the clips, they pop off like rockets. There's about 5 or 6 of them. Then pull the trim from the bottom outward and upwards. You should be able to slide it out from under the rubber mould that runs along the window edge. Navigate the seat belt through the gap in the trim.
2. Preparation
Now you need to get someone with small hands to wipe all the dust off with a damp cloth. I used Karcher pressure cleaner. Takes some time to dry tho. Get some rags, gloves, and long sleeve and goggles also recommended. That toxic stuff does not wash off with anything! Took 4 days till it washed off my skin. Next step is most fun.
3 Application.
3.1 Read and follow the instructions on the can. Should be done in a well ventilated area.
3.2 Apply the foam to fill the all the gaps where the smog can get through. But try to avoid filling the very bottom of the cavities. Moisture will get in there. At the very bottom there are holes for ventilation they should not be blocked or you risk rust.
Note: Foam expands up to 3 sizes of a can when drying so don't get fanatic.
3.3 Let the foam settle and check for any gaps. Fill any remaining gaps and give some time to till the foam is hard. Road test it. If needed repeat step 3.3.
4. Completion
Clean the trims on inside and assemble them in a reverse of step 1.
That's it you are done! No more diesel smell or dust.