Do not go cheap pattern parts rarely work or last long, always go oem brands Bosch or Seimens. Going to hurt the wallet but assured oem will work out of the box. Learnt this lesson very early on with my 1.9 Z3 felt like it was being held back and lumpy running. Put a Bosch unit on and it instantly cured the problem.
Same could be said for all other sensors on the Z3 and Z4 but I have had success using Hass brand camshaft sensors.
The old addage buy cheap pay twice was never so true when it comes to sensors.
I did try cleaning the original with Maf Cleaner, all that did was kill it completly.