Eclipse Gst Not Firing

I just bought an 90 eclipse gst its my first turboed dsm out of the four that I have owned.When I brought the car home on a trailor that man I bought it from told me that he thought that the engine was ruined...well he was wrong it cranks up the turbo boost 16 pounds but the prob is its only hitting on two cylinders.My question is what are the ways I go about finding out why it is doing this.It could possibly be the coil pack but what else could it be causing this problem?
Thanks for the Info

which two cylinders ARE firing? i would think its the coils/plugs... if they are from the same coil, replace the coil. if not, check the compresson and change the plugs.

cylinder 2 & 4 are not firing.
I will replace the coil and plugs and see if that does any good.
Oh and one more question off topic....there is a hose running from the motor its a small hose that some one capped off.What the hell is it for? lol