I installed the F-Sport lower airbox filter ealrier and the sound has greatly improved. It's much more entertaining to drive the IS350 now.

Would I get even more sound if I replaced the standard Wix air filter and the rubber intake pipe with a high-flow air filter and a metal/hard pipe?

Or did most of the sound improvement come from just the lower airbox in the complete F-Sport intake kit (which includes the lower airbox, air filter, and hard pipe)?

 

The metal pipe will probably enhance the sound a little opposed to the rubber pipe. Though you'll gain some performance with the metal pipe too.

As for the filter I think stock filter performs best.

 

I have a factory unmodded airbox with a K&N panel air filter in there. It definitely makes additional noise over factory replacement panel filters. Plus, according to K&N, additional ponies due to the increase in airflow (CFM).

 

If you want noise. You can also install 14+ IS350 F Sport intake pipe with speaker (not sure what that part call). I install F sport air box, AEM filter, and 14+ IS250 F sport intake pipe on my IS250 and it make my engine sound louder after 3,000 RPM.

 

Ended up buying one of those actually from a 4GS, dimensions appear to be the same. I'm assuming the metal clips on the ends of the tube, along with the tube near the sound resonator are all reused?

 

Yes, I reused my metal clips.