How do you get the Stevie missions in GTA IV?

I've played through this game twice, once when it came out and again almost a year ago, and in both, I completed all of Brucie's missions*. When I was reading about some of the cars that are going to be in GTA V, there was a note about one of them having been one of the cars you needed to steal for Stevie in GTA IV. I was never given the opportunity to steal these cars, nor can I go to his shop to sell stolen cars. According to what I've read, the only thing you needed to do before being introduced to Stevie is to steal all the cars that Brucie wants. But I wanted to know if there was more, like completing all of the races or liking Brucie 100% or if it had to be done while I was still doing the main campaign?

* Going to the stats menu tells me that I'm 100% on completing Brucie's missions.