Originally Posted by Twenty
They don't (but I haven't had to make any claims yet, knock on wood) but I don't want to push/risk it. I installed my Steeda sway bar there, but I'm not worried about suspension, only powertrain. We all get along there so I'm sure they'd cut me some slack, but I keep a healthy respect for certain warranties.
I wouldn't sweat it too much, honestly.
In the US, (thanks to the Magnuson Moss Warranty Act) to deny a warranty claim due to aftermarket parts, they would first have to prove that a specific aftermarket component caused the failure in the first place.
If anything, a stiffer rear mount should prolong the life of the other two motor mounts. I'm not sure if there's an equivalent of the MM act up there, but I'd look into it if you're really that worried.