Howdy, new to the Forum. Hopefully someone out there can lend a hand. Purchased an 07 R 320 in December of 2013. I am still getting to know our car. I just noticed that the top most idler pulley is smooth. The grooves of the belt ride over this. The belt is routed correctly. The lower idler is smooth and the back of the belt rides over it as you'd expect. I have searched all over the internet and nowhere can I find a grooved idler for my car, they are all smooth.

Is the top most idler supposed to be grooved or smooth?

I certainly appreciate any help. Thank you