i always thought that aftermarket parts do not void warranties, unless they cause the problem. but the guy at the exhaust shop told me a high flow cat and headers will loose it completely for me. is this true? please help
Truthfully, Cat-back, you're fine. Intake (CAI or SRI) you're fine.
Headers... that seems to be where Hyundai draws the line on the powertrain warranty. While Magnusson Moss does provide that the manufacturer must prove the aftermarket part caused the failure, the more involved the part is with the basic running of the car, the easier it will be for them to claim your part caused the failure. So, you can go with headers, but expect a fight if you need to claim warranty repairs if have engine problems.