I have a bf2 xr6 turbo with the under pulley kit in it now for two half years. I only got it because I did not like the plastic ford ones. At the time it seemed to rev quicker not sure of power gain. I have had no problems with air conditioning or power steering at all. Just had it tuned to 323 rwkw the past 2 months. Wow from standard to this love it. Still no issues. Just my 2 cents worth. If they damage the engine I would like to know how as well.