I have put on approx 40k miles on my 03 mcs in two years with no problems. About a month ago I noticed no low end power as if starting in second gear-like a slug. Two weeks after this the crank pulley went. So, I upgraded with pulleys, cai, springs, and sway bar. The low end power is still not there after the repair and upgrades. Currently no codes other than flat tire sensor. Any help would be appreciated. Any easy diagnostic tests would be great.....Thanks