The little plastic tops that usually are on the top of injectors (fuel rail side). If they're gone will it hurt flow that much? I have 8 240cc injectors and I'm about to send them off to be cleaned, and I wondered if not having the tops on is a big deal. They worked when they were in the car

 

Are they just one more type of filter?

 

Yes,they are filters.
When I sent mine at Rc eng,they used an other type of filter.They are inside and made in metal compare to OEM,in plastic.