GTA now in
Join Date: Sep 2015
Know I'm a bit late to this discussion, but the resonator definitely made a difference to the Peugeot 306 GTi6. It effectively had two, one on the inlet manifold and one on the standard air box. Somebody did a dyno test with the standard air intake removed and a k&n fitted, and there was a 2-3bhp drop in the mid range, and with both resonators removed you could actually notice the flat spot when driving. But that car did have pretty much everything factory tuned to give it a flat torque curve, so that was probably the exception rather than the rule. Did Alfa change the design of the inlet / exhaust manifolds and valve sizes when they added the resonator? If not, then it probably is just a noise reducer.