What kind of milage did you put since the clutch install? I hear at least 300 miles at varying speeds to break it in... last thing you want is a glazed flywheel. a slipping clutch with show you it's slipping when you get on it,usually the rpm jump up, and you're not feeling it pulling...do you know if they machined your existing flywheel before the new clutch install? If that was my clutch being installed I would def have machined the flywheel... there always is a glaze from the original clutch,leaving that glaze on and having it combine with a different friction material,potentially not compatible with one another can easily alter how a new clutch breaks in...a good level of prep to BOTH clamping surfaces is always the safest route to a great clutch break in.