Alright well I have an 84 GSL-SE. I washed the engine bay today, and now it bucks over 300 rpms when I drive it.

Is this because i may have gotten electrical stuff wet, or did i get water in somthing that shouldnt have water there?

 

Pull the distributor cap off and blow it dry inside.Probably a good idea to pull the sparkplug wires and blow them out on both ends too.
Its almost always the dist. cap that gets wet inside,then you get spark scatter and tons of missfires.

 

Yeah, i did that a few times, still didnt run right.

Now i have another problem, the battery is dead. Can it be boosted safley withoput cooking the ECU? Or can i use a battery from an na S4 FC?

 

You can use any car battey you want, as long as it's 12 volts.
As for the problem, I'm thinking vacum leak is more likely than electrical...