2002 ls Tahoe vin code z misses only at idle

[Chrisqo]

2002 vin code z Tahoe misses in cylinder 5 only at idle intake gaskets are new 3 weeks ago, new plugs new wires, I've tested the voltage at the injector and its the same as the 2 next to it, ohms is the same as the 2 next to it as well but if I unplug the injector the rpms don't bounce around like it does with it plugged in anyone got any ideas