I have bad engine noise that gets louder as I turn the gain up on my McLaren MLT-2 tweeters on my PPI 900.4. Is it a car issue or maybe an issue involving the amplifier? I've heard it can come from either one but I rewired by entire car and made sure I got good solid grounds but it didn't help at all. I am going to test to see if it is the RCAs tomorrow when I get home from college and if so, I'll order some new ones.