Help. My 1999 mustang gt will start and idle but will not rev up at all. I did a smokey burnout on my way home from work. When I got to the house it was low on gas so picked up some gas and filled it with about 5 gallons. After that when I started it it would not rev up and threw four check engine codes. P0300, P0161, P0156, and P1504. I have some modifications done cold air intake, underdrive pulleys, short throw shifter, 3.73 gears, and comp cams xe262ah installed. Any information would greatly appreciated. I bought this car new as a birthday present and I am the only one who works on it.