After replacing the air filter with an A'pexi one, I still left that thing that is like a flattened duct from the middle that goes over to the intake area. Is it still providing any extra flow, or should I just can it?

 

I doubt if it is providing any real benifit at this point. If you had a way to keep all the other hot air from the engine bay away from the filter, it may be helpful.

 

I leave it on, it looks better. no performance as far as i know.

 

I took it off and mounted my MSD there. No, it is not adding any performance advantage. It never did.

 

When it was attached to the airbox it did make a difference. It stopped the hot engine bay air from being inhaled and it lowered induction noise (that's what the empty volume tee'd into the side is for). Without the airbox it's redunant.