I got a friend just done his ICE setup recently. There are one 4ch amp, mono block, 2xsmsc sub and a pair of component set. After installing the system, some serious problem start to show up. Firstly, the head unit (original) will lag sometimes, mostly happened when he try to shift gear especially reverse. Secondly, he found that the headlight will dim when he shift gear or reversing. And lastly, the steering wheel will become heavier during shift gear.
By him telling me that, I am guessing bad electrical system or bad grounding. But the car is less than half years old. Any sifu there experience these symptom before? What is the causes of these problems? Helps and comments will be appreciated! Thanks and have a nice day!

hi, may I know how old was your car when u face that problem? tq very much for the respond