Outer Limits 4x4 Board

Gday 2 questions for you all
vehicle is a 93 NJ pajero 2.8ltr TD 4M40
1) have a vaccum switch thats located on the passenger side of the engine bay towards the top of the firewall, one vac line goes off to the other side of the engine and hooks up to where the brake booster hooks into the vac pump and the other side of the switch i dont know where its ment to go. any help there would be good? also whats the switch for as i couldnt find it in any manual.

2) What do you guys do for air filters. i am sick of the stock filters and K+N dont make a aftermarket one. what do you replace yours with?

Thanks

here are some pics of the vac switch

I had a 2.8 4M40 witha K & N filter about 4 years ago.

The vacuum thingie, I seem to remember seeing wires from it going to the intercooler fan so it may have something to do wiht that??

As far as the air filter goes, i say stick with the stock paper one. I ran a finer filter in mine for about a year but ended going back to stock. K&N's are great for power but p!ss poor at keeping dust out of your engine.