I wouldn't recommend using metal for your intake pipe as it will just soak up all that exhaust heat and defeat the purpose. You can search around some of the aftermarket speed shops and see if someone has a tapered non metallic that has those dimensions on the end but I'd just stick with the stock
one, or get a reducer to fit the top one. You can see what I mean here, look at the fittings.
http://www.simota.com.au and click on the fittings.
You have to take in consideration the small hose that goes to the rack and pinion from the bottom of the first boot from the AFM.
Just get rid of the airbox and add a filter like the AEM or Simota. You will need an adapter for the cone that attatches to your AFM.