usually they close one eye on such things. but disclaimers will come out if say you have an unexplainable electrical problem or cracks around the reverse sensor bumper holes (they can point to the reverse sensor) or if your cat converter prematurely spoils (even though nothing flows backwards).
so rule of thumb is, if warrenty issues arise on items directly related to the aftermarket part, then no go, depends on how strict they are. Much less to say no warrenty on the aftermarket part itself. they will still honour the warrenty for the rest of the car, generally.
however pls be reminded that they are just being nice, coz they have a right, on black and white signed, that if anything non-original is fitted, or if anything original is fitted not by PML, or if your car is serviced outside before, to void your warrenty altogether.
usually they are pretty nice about soft mods.
many ppl have asked the same qn over and over again, so maybe we should point them here in future.
louis, usually when qns are asked more than a few times before, ppl dont reply anymore. hahaha