Upsie-Daisy. The Adventures Of Lee And Bucky

Auto mechanic Lee Singer considers New York City her personal playground, with lots of big engines and complicated tools and today a car that got towed in because those "severe tire damage" signs mean what they say. It only adds to the fun when she pops the trunk and finds it full of styrofoam heads. It turns out the client isn't a madman with a decapitation fetish. Instead he's a marine roboticist, and if you send foam objects down to the ocean floor, they shrink under the pressure.
Wait, he builds robots? And he's hot? This requires definitive action. A little verbal sparring ensures that not only is he going to take Lee to dinner, but if their date goes well he might just show her his hydraulic manipulator arm. (That's not a euphemism, by the way. His team actually has a submarine in a warehouse near the West Side Highway.) This Lee and Bucky novelette takes place about four months before the first full-length novel, so whether you're new to the series or just teetering on the edge of a great fiction discovery, you'll have a great time. Jane Lebak is a novelist and humor writer who pays someone else to change her oil and has never made a shrunken head.
This story is also included in the anthology Where The Light May Lead.