I have a 2000 V6 sonata, has had a problem that has slowly got worse.

Missing and popping sounds like a lean fuel air ratio condition. It should set a Check Engine Light for the misfire. Is the Check Engine/Service Engine Soon Light on? If it is or not a professional grade scan tool you can look at key engine data like fuel trim figures to see if the engine is actually running lean. If the plugs haven't been changed in a while it would be a good place to start. Your car's engine has hydraulic lifters so valve clearance is not an issue. Make sure there are no manifold vacuum leaks. Hyundai as a car manufacturer put a lot of free technical information and workshop manuals on line for Hyundai owners. Check out www.hmaservice.com lots of great information.