This link from the Federal Trade Commission addresses your question. It explains, in layman's terms, the Magnuson-Moss Act.
http://www.consumer.ftc.gov/articles/0138-auto-warranties-routine-maintenance
Note the section about after market parts; which is what you are referring to.
Keep in mind, what the language fails to be very specific about is whether an aftermarket part needs to meet the original part's specifications. Just for the record, it does have to meet the specifications, and most often the language in the warranty states something similar to that fact; which is allowable by law (and only makes sense -- otherwise consumers could do anything to a product and then try to make a claim).
However, regarding an aftermarket part not meeting the exact specifications or specific language of the warranty; the Magnuson-Moss Act will limit your liability to the exert of the aftermarket part itself, and any related damage/failure it may have caused. All other parts the warranty covers remains in effect. And the act requires the warrantor to prove the aftermarket part caused the damage.
A manufacturer proving the extent of the damage, its cause, and its limitation of liability can sometimes be difficult to do; and when these cases get complicated and sticky (due to a severe situation); typically a large corporation has deep pockets and a staff of attorneys ready to take the case to its fullest length -- requiring you to defend yourself in court and wait for the process to come to its conclusion.
Most often when the situation gets to that point you are without your vehicle (or product) and spending money on legal fees while waiting. That is when you hope for some sort of "out of court settlement" to occur if you are in a hurry; otherwise you are in for the long haul whether you are right and protected by law or not.
So, when people quote the Magnuson-Moss Act, keep in mind, there is not a steadfast form of resolution to a problem. In other words, there is not a "800-Magnuson-Moss-Act-Complaint-Hotline" you can call to demand the manufacturer come to a resolution immediately.
It is not often it goes this far, but when it does, it becomes a real hot-mess (as my son would say); and since you asked, I felt obliged to let you know all the potential circumstances.
All in all... I would find someone to put the sway-bars on and go about enjoying your Spyder.