They have a number of flaws. Here are the most common complaints. Cylinder wall chipping, poor tolorences in machining. vacuume leaks at the base gasket due to transfer port misalignment. Poor threading on the intake and exhaust studs. The manufacturer has already stopped production on this kit and all of the dealers have know this for about 2 months. It is pretty sad because the US distributor will take returns on them but most dealers would rather continue to sell what they have for a profit than return them and just get their money back.