I bought this car from my buddy. Been driving it around for few weeks. Ran great I decided to put after market cd player , amplifier and subwoofers in it. Got it all installed then turned to key to start it and now it wont run. If I keep my foot on the fuel pedal I can get it to stay running but very rough. Wont rev up or anything. I can put it in gear and it will move but wont go over 3 or 4 mph . I then pulled the cd player and everything back out of it thinking that would help but got same results from car. Some people told me if the battery drains a little it will derate computer. I am totally lost on what to do and which way to go toward fixing the issue