1. Warranty has nothing to do with your intake.
2. A better filter might only get you 5hp, but it will increase throttle response and, if you're lucky, get you an extra mile per gallon. It's $20 to stap a 9" cone filter on your mass airflow sensor. Do it; it won't hurt anything to do it without a tune, though a tune would increase the benefit from it.
3. Whine is the high pitched noise a supercharger makes, but is muffled by the big honkin stock box intake. It sounds like your car unzipping its pants.
4. You will see increased benefit from exhaust work. Fortunately for you, GM saw fit to give you a cat-back exhaust system with nigh-infinite flow. Well, not really, but you'll never outflow it (unless you turbo). The best thing you can do is to buy $220 Speed Daddy headers from eBay, upgrade the clamps, and install them. Short of that, a 3" catted downpipe from one of the w-body vendors will suffice (the benefit being that it is slightly easier to install than full headers). You do not need exhaust mods at your modification level but you will definitely benefit from it.
