That looks like a power steering or oil cooler line. Runs in front or radiator?
It is like a cooler Ali. From twin cam S13/14. You can replace it from a parts car(Rob-DrumFunken, might have a good one). Or you can replace it with and external cooler.
I think it might be the low pressure return from the rack back to the reservoir. I just ran a transmissionpower steering hose from the rack to the reservoir. Eliminated it.