As far as i know, my system was installed by a very reputable shop and you can see that through the website they have.
By saying, "if the system isnt installed properly..." are you referring to making sure the last thing you hook up is your RCAs, after your battery, REM, ground and speaker wire are installed and hooked up? AND ensuring your battery wire and RCAs are not run together?
If you dont know what engine noise is, then you dont have it. It is obvious, and easy to hear. It is directly related to your RPMs, not your volume of your headunit. So as you increase RPMs while you accelerate, the noise gets louder, and then it becomes quiter when you change into the next gear until your RPMs increase again.
Noise filters and grounding your RCAs do not always work. My girlfriend has a noise filter, there is still engine noise, and its still obvious, but not as bad. And grounding your RCAs is not going to solve the problem 100% of the time either.
That is why, I will never own a pioneer ever again. I will get an alpine, so this problem does not arise. the prices are the same anyways. Kenwood decks are good too.