For my slightly upgraded 9-3 SE, this is an excellent, high value upgrade. I had it installed with a new Viggen clutch and the GS sport transmission mount. Immediately, I perceive a significant improvement in engine responsiveness and torque output. Slight but perceptible increase in fuel economy as well.

It changes the shifting dynamics a bit, due to the lower inertia. Engine revs down fast once you disengage the clutch and let off the throttle. So it requires a few days of adjustment before shifting feels smooth again.

This is one of those rare upgrades where you gain power without sacrificing fuel economy. It just makes your engine more efficient. It's a must-have AFAIC. Slip one in when it comes time to replace your clutch, along with the sport tranny mount.

Rating: [5 of 5 Stars!]