What is the tube between the air box and plenum called?

[ChrisZang]

So I finished my little DIY hi-flow intake project
I cut the original intake next to the Helmholtz resonator and replaced the part with a 45 degree silicon knee from eBay ($20) (see picture)

Results:
a) Performance gain/loss: No gain and no loss
I did 4 timed 30 to 60 runs in 3rd gear with same results before and after

b) Sound:
Not a dramatic improvement, but the orchestra that starts playing in my intake above 5,000 RPM has added at least one more Trumpet player to the mix

So overall, not bad for a few bucks