Factory warranty is 3 years or 36,000 miles (whichever comes first) bumper to bumper warranty, excluding normal wear items, and 5 years or 60,000 miles on the engine and drivetrain. GM will sell you an extension, to take the bumper to bumper warranty out to 5 years / 60K miles on the day of purchase only. You can't add the extra bumper to bumper warranty later. GM and others offer service contracts, sometimes called extended warranties, that can be purchased later. There are several threads on the forum about those.
The basic answer is that no mods will void the entire warranty. Well, I suppose if you turn the car into a full racer, and rip out all the things you don't need, like the infotainment cluster... Mods can cause GM to deny a specific warranty claim if they deem the problem to have been caused, even in part, by your mod.
But any single mod will, at most, affect the warranty only on issues related to the mod. So if you supercharge the engine and change out the entire exhaust system, and then the radio dies, the warranty on the radio shouldn't be impacted. But if you do that and burn up a valve, or eat a piston, bend a con rod, or snap an axle, GM is just going to laugh at you if you try to file a warranty claim.
Where it becomes sticky is if you have a problem that isn't caused by the mod, but could even remotely be related. Say you change out the exhaust system and then have an engine problem that isn't really caused by the exhaust. But when the dealer files a warranty claim, they inform GM that the exhaust isn't factory. GM could use that as an excuse to deny warranty coverage, and then your only option is to pay out of pocket, or sue GM. GM has a whole legal department with tons of experience fighting these kinds of cases. Good luck.
As a general rule, figure any changes you make to the engine or drivetrain to make more power put the engine & drivetrain warranty at risk. GM can say "we designed part X to handle 495 HP, not 525 HP or whatever, so the failure is the customer's responsibility." A warranty claim on a modified engine might not be denied, but that possibility always exists. If you've done major mods to make lots of extra power (e.g., a turbo or supercharger), pretty much throw the drivetrain warranty in the recycling bin.
