Engine Electrical Problem???????

Problem is when i turn my left blinker on the brights come on and when it goes back neutral they go off,so if i barely tapp the light switch down the brights wont come on,thats my first problem second problem is i just recently had a system installed in my car amp and a sub and it seems ever since when i turn the headlights on the rpms go down and i idle way to low????????is this electrical or what? is it the switch? or the system?
I have a 1992 toyota paseo that i just bought like three weeks ago so i am new to the car,just last week i replaced fuel filter spark plugs wires valve cover seal had the injection system cleanedhad it diagnosed ?

I have the same problem with my 92 tercel. The two are more or less the same car. My brights come on just as soon as you start to turn the wheel to the left. I have to pull back on the blinker just a bit to keep from flashing anyone.