(I have a V6 Probe)

One day my car kinda made this spudder, and it got worse and worse and my dad said a cylinder isn't working. Well we pulled out one plug wire at a time and the car idled down, untill we pulled the back left plug wire. The engine made no change, it kept idleing bad we put the wire back in and reved it up and pulled the same wire out again it still made no change. So that cylinder wasn't fireing. Eather no air or no fuel. So we did a compretion check, all six cylinders were remotely the same.
Well I road it around for a while on just 5 cylinders, cause I didn't have time or monney to fix it right away. Then one day i bought an injector and replaced the injector on the one cylinder, the car didn't miss anymore but it still spuddered real bad.
So its getting spark cause we pulled the spark plug out and started the car and it sparked.
its getting fuel because I replaced the injector, and the car doesn't miss as bad. So the only thing left would be air. My dad thinks that a valve is stuck or something. Does anyone know whats up??