When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The std WRX OEM paper panel one and OEM intake box/trunking is quite efficient and will see you to about 350bhp, before you need considering something else.
So good news, you don't have to spend out in this area just yet.