My 2003 has just over 100K miles. The engine is not makeing any unusal noises during idling (knock-on-wood !). However, I am planning to change the lower timing chain tensioner as a precautionary measure. I found there is the genuine BMW part that runs over $130 and then there is one made by INA and it is about $98 and it is referred to as OEM part. What's the difference between these two parts ? Anyone with experience ?