I have a 2000 EX (D16Y8). With the car all stock, it's very difficult to tell, but if I remove the resonator (a plastic box with a big U shaped tube attached to it) and keep the stock airbox and filter in, then you can definitely hear a change in intake sound at around 4900 r/min at WOT. It's nothing like a B16A, but you can feel it "pulling" a little longer than you'd expect, as the non-VTEC D16 engines level off after about 5000 r/min.