I noticed a difference when I changed from the ruined pipercross filter that came with the car to a standard airbox (with no extra holes).
The low end torque was improved but the top end wasn't as good. It would probably benefit from a session on the rollers, but it's good enough that it wasn't worth the hassle.
And you could also sit on the motorway at 60-70 for longer than 30mins without your ears bleeding, 
