I have a 05' Monte SS Supercharged and at an idle I hear a slight high pitched faint whistle noise. I recentley had the super charger oil changed at 35k miles. Haven't had the car that long and was wondering if this noise is normal/common?

 

I believe there is a vacumn leak somewhere. I'm not a tech, so I'm guessing. Hopefully someone more knowledgable will chime in. If it is a leak, get some carb cleaner and spray it in the ares that it's coming from. It will temporarily stop whistling when the leak gets wet, and the carb cleaner won't hurt anything.

 

x2 on it being a vacuum leak. Inspect your vacuum lines and fittings- are any cracked or broken?

Connect a vacuum gauge to the brake booster vacuum port while the engine is idling- you should see a steady 19-20 PSI of vacuum at idle. If vacuum is significantly lower, or if it's fluctuating, you've got a leak. Auto parts stores sell vacuum gauges for $10-20. They come with easy to understand instructions.

The carb cleaner method is an old trick that definitely works. When you hit the leak location with the carb cleaner, you'll hear your idle become faster by 2-300 RPM. Careful with the carb cleaner around hot exhaust manifolds though- it's flammable.