I have a 2006 GTX that after having valve cover gasket/plugs/plug boots replaced, no longer has the “pop” or acceleration it had before the work was done. The repair facility has indicated that perhaps the supercharger has failed. Starting and riding is easy with no strange noises but as stated, the power band is no longer there. Pre work, speed was 60mph, post work, top outs at 40mph. Everything worked before the shop got it but now it's different. They are checking but curious if it could be something else.