So the OEM BMW harmonic balancer is almost $700.
febi/bilstein is under $200. Okay to go aftermarket here or should I stay OEM for the crank pulley?

car is at 140,000mi. Going to do the belts and pulleys as preventative maintainence.

 

Febi is the OEM part. It's not aftermarket. It's $152 for the part

 

thank you, same deal for the tensioner pulley? Is the INA brand $40 cheaper cause it sucks?

 

With BMWs, it's always best to stick with OEM.

 

This is the right answer especially since it's a major part of the engine. Don't cheap out on the parts that make your car run. You'll end up spending more time and money than you need to.

 

Is Febi/Bilstein the OEM belt tensioner pulley as well?

 

Which one? There's 2 tensioners which are usually sold as an assembly. My go to for tensioners have always been continental

 

One of these three
https://www.fcpeuro.com/products/bmw-belt-tensioner-pulley-11287542680

https://www.fcpeuro.com/products/bmw-belt-tensioner-pulley-febi-21629

https://www.fcpeuro.com/products/bmw-automatic-belt-tensioner-assembly-11287549588


I see they have the kit you are referring to.
https://www.fcpeuro.com/products/bmw-accessory-drive-belt-kit-adk0024p

 

The kit you posted isn't a continental tensioner but it will do if that's the route you want to go.

Continental has a kit (CONTINENTAL ADK0024P) that's on RockAuto