I am a mechanic, and here is the deal yes it could be a bad injector that is leaking down not closing, but you said you are down on compression, if the valves are over tightned than the valve might not close when you are doing a compression test . A 100% test is a leak down test and than you have to back off all the valves cause there can be no lash on the valves. A valve lash should be done hot also and maybe if you want change injectors from one cylinder like take the #1 injector and put it in the bad hole .