RULES ON MODIFICATIONS (Performance Products)
Allowed or tolerated modifications
Changing wheel size; the outside diameter of the tires must be comparable to the original diameter. Adding a stylized skirt. Installing a solidly fixed aerofoil, so long as it is not wider than the vehicle and obstruct the lights. Changing the seats, so long as they are fixed onto the rails or original anchors. Changing the muffler or any other component of the exhaust system. The exhaust system must be solidly fixed, not leak and be designed for on-road use; it must not be noisier than the original. Increasing the engine's power output. Changing the bumper shell. That part of the bumper, designed to absorb energy in the event of impact, may not be removed nor modified.
Prohibited modifications
Remove or deactivate an airbag. Modify the windshield wipers to reduce the cleaning surface area they originally covered. Alter or remove a seat belt or its anchor from the original installation. Change the color of lights or reflectors by substitution with a color other than that allowed under the Highway Safety Code. Reduce the brightness of lights or reflectors by the addition of darkening or opaque material. Install tires not designed for road use, such as racecar tires or oversized ones that jut out from the vehicle's fender. Reduce braking capability by installing disks that have been handcraft drilled, for instance, or using non-standard components. Using springs that have been shortened, bundled or heated to deformity. It is also prohibited to have a suspension that is too rigid, an insufficient wheelbase, tires that touch a vehicle component or having any part of the vehicle body touch the road surface in a normal driving situation.

(SOURCE: SAAQ)