I've heard the same thing about the throttle springs also that they should be in front hooked to the top. I've just never changed mine.
I also have the Wagner adjustable PCV valve.
The air filter I found on Amazon. I figured it has about 20% plus more filter area then the large oval one.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
https://www.summitracing.com/search/...rder=Ascending
Scott