on mine I had misfire codes on 4 and I changed the injector, then retested and had code for 2&5 so I changed those, it was while changing them that I noticed the vacume hose going to the evap being snapped off, I am wondering if that was my problem and my injectors were actually ok.
from my Haynes manual talking about the EVAP (Page 6-16)
Poor Idle, Stalling and poor drivability can be caused by an imoperative vapor managment valve, a damaged canister, spilt or cracked hoses connected to the wrong ports.
So the evap can cause the same symptoms as misfires in the cylinders. not saying that this is his problem at all, but still worth checking.