GenghisKhan

I have an 04 ls1 that stalls/floods when I leave it idle for too long. The guy I bought the car off of, unplugged a solenoid cable for the skip shift so that the car could shift through all 6 gears. Now the t/c doesn't work, the abs light is always lit and it floods. Just today I was driving home from work, cruising at about 1800rpms and then stopped at an intersection, after about 2 minutes, my rpms start fluctuating from zilch to 3k and then shutdown. I turned the key and depressed and pressed the clutch and had my foot to the floor, after a few tries it started and I sped up and it started jerking spontaneously. As I sped up it jerked a bit more then returned to normal.

With a code scanner I got p0803 for the skipshift, but I don't think that would cause my car to stall randomly and sometimes if I park it for just a bit, the engine won't start, battery works though.
Whys my car stalling yo?