denso 550cc question
 

My new injectors have a bit of a different shape to them than stock. In the picture, the top two are Denso 550cc, and the bottom is my NB2 stock injector.

The stock injector has a rubber grommet at the bottom of the part of the injector with the o-ring that fits into the fuel rail. As you can see from the photo, if I place that grommet onto my Denso's, there's only about half as much injector to fit into the fuel rail.

Do I need to use that grommet? At the moment I have the Denso's installed without them. Even with motor oil lube, they fit very tight, and didn't seat all the way until the bolts pulled the rail down onto them.

Advice appreciated. Thanks. I have new grommets to use if I need them.

I have now spoken with people who have installed Injector Dynamics injectors, which have a similar construction using a machined aluminum spacer, and the upper grommet does not get used on them, so I'm moving forward with the denso's installed as is.