I think the question boils down to whether you are trying to shake the tail or outrun him. Stunts are good for trying to lose him, breakaway is simply for outrunning. In either case, I think that the motorcycle rider would have to make a Vehicle test every IP in order to keep up. The difference is:
Break Away: Reaction + Pilot Skill [Speed or Handling] (maneuver threshold) - You gain a category for each hit and the other driver can choose to spend a complex action keeping up. If you leave Extreme Range, the opposing driver gets one last test to see if he can keep you in sight. I'm guessing that the limit in this chase is Speed since it is largely open highway. Base limit is 3 for the Americar, increased to 4 by your Control Rig. The biker has a limit of at least 4 (assuming they aren't on Dodge Scoots). With a maneuvering dice pool of 12, your limit is a problem.
Stunt: Reaction + Pilot Skill [Speed or Handling] (maneuver threshold) - If you succeed, then the other driver has to make the same test and threshold or drop one Chase Range category. Again, they have the limit advantage, but it might not matter depending on their dice pool.
Another option, if you drop back in to short range, is to try to force him to crash with a cut-off action. This is a direct opposed check, and if you win, they have to make another vehicle test with a threshold of your net hits. Because of the low limits, this is probably not a great option for you.
I haven't seen the opposing driver's dice pool, so it's hard to determine what option gives the best chance of success. But the best play seems to be to keep him busy with Vehicle Tests while Sabato takes potshots and hopefully takes him down. Hopefully he'll choose to break pursuit before expiring, otherwise we get the attention that leaving bodies behind tends to draw. Of course, shooting in public in broad daylight in a place where guns are all Forbidden is likely to draw a considerable amount of unwanted attention anyway, so hey, in for a penny, in for a pound.
