A ground strap is to ground the hood. When you're driving, the friction between the hood and air can cause a build up of static electricity. A ground strap grounds it so the charge can't build up and arc.
20x25x6 filter in our system, changed at 6 months with 3 cats in the house and mostly hard surface floors. Filter looks darker for sure but never seen it look so bad I thought it needed changed sooner then 6 months.
Like Pew said, factory intakes are designed to muffle intake/turbo noise. This did make me think about when I learned how to flip the air cleaner cover on my dad's 69 Pontiac 428ci motor, made that great intake roar after doing that!