blowcane

im having new issues of my car not reving past 5 k runs perfect up to that rpm though idles alittle rough so first thing I started looking at was ignition while I had the car running I pulled the plug wires 1 at a time to see if the engine would run rougher wires 1 and 3 seemed to have little to no affect while 2 and 4 made the engine almost die the next day I started it up to do more investiagating and noticed my afr went from a 14.6 the previous day to a 10 this time did the same thing pulled plug wires 1 and 3 both at the same time and left them unhooked looked in the car and my afr was back up to 14.6-14.8 why would it run leaner with 2 plug wires not hooked up it should run richer dosent make sense to me hopefully someone can shed some light on this would really like to get this thing tuned and done