so when u fitted it did u disable the viscous coupling or are you running the electric fan in conjunction with the std viscous cooling system?i have done this on my 200TDI and used a 14" fan from ebay, it's on a switch. i did a days laning on sunday and never switched it on. only every used it if the car is sitting still for some time. last time was it's MOT
One thing I would suggest, get the correct mounting ties that go through the radiator, makes it a very simple job.