Are the spider injectors supposed to have sealing o-rings on manifold ends? on 1995 Chevrolet S10

my uncle's s-10 4.3 vin "W" is having a miss in cyl #2. He recently had the inj. assy. replaced. He says the injector nozzle doesn't fit snug, but locks, in the hole. Should there be an o-ring there? He says it doesn't have one.

Asked by for the 1995 Chevrolet S10
no, it just snaps in. where the injectors are is a vacuum chamber already.

Thanks Roy, I didn't think they did. Just wanted to make sure.