Dumb C70 question

[Doug in Denver]

I justy bought a '99 convertible, my first Volvo since a '74 164E 20+ years ago. On saturday I was replacing filters and checking fluids, etc. Here's my question. Under the hood on the passenger side, nestled between the filler for the windshield washer fluid and the power steering fluid reservoir is a large black plastic box about half the size of the battery with a flat oval air hose leading in and a round hose going out that goes through the firewall. OK, what is in the box? What is its purpose?

[dosbricks]

That's the ECM (Electronic Control Module), in other words it's the car's computer. I bet you didn't have one of these on your `74 164E

By the way, no question is dumb if you are a new owner or never faced the problem before.