"In this Special Series about the Mechanical Restoration, I document the repairs, the replacement parts and the mechanical upgrades to the E46 M3. 

In this entry, we install the Performance Power Steering Reservoir into the Phoenix." 
-Matt

The E46 had to be different.  

In the previous entry "American Execution", I mentioned the Performance Power Steering Reservoir was designed as a replacement 2x original BMW SKUs: 32411097164 and 32416851218. 

From what I gather, it will fit the E30, E36, E46, E34, E39, E60, X3, X5, Z3, E82, E9X, E84, and E83. 

Pertaining to my cars, the V10 already had a fix, the V8 wasn't leaking - but the E46 was. I opted to document the installation of the demo unit on the Phoenix as it also presented relative challenges with the CSL airbox. 

The S54 is usually pretty easy to work on - with ample space in the engine bay relative to the S65 and S85, except for the power steering reservoir. 

For reasons unknown to me, BMW opted to lodge the reservoir under the original airbox and its CSL counterpart. 

Imagine having to fill your reservoir frequently by removing the airbox, and throwing away the original one time use ITB clamps. 

Can you see it? Right behind the alternator (!). 

The reservoirs in the V8 and V10 engine bays are held by 2x bolts - this.. wasn't bolt 2x bolts. 

The unit is held by a clamp going across the body of the reservoir.

Said clamp is then bolted to the chassis. We removed the clamp first. 

The clamp got unbolted to be transferred over to the new reservoir. 

Does it fit? There are two challenges. 

The first were the angles at which the fttings came out form under the reservoir. The original has short, and straight out from the bottom. This unit uses the E9x M3 angle. 

You need to fiddle and position the reservoir properly. The power steering lines aren't exactly flexible: the angle needs to match to avoid damaging the hoses.  

Next was the clamp itself: the performance reservoir has a slightly larger body compare to the original unit. As you bolt the clamp, it all comes together for a secure fit. 

I tested fitted the CSL airbox: it fits! There's proper clearance.  

We filled up the reservoir with ATF fluid, noticeable by its red color. Don't follow this advice. 

Topped off, and ready for its cap. 

Nice. 

So, is it worth it over a 30$ OEM replacement?

Leaks suck.
Whiney power steering sucks even more. 
Removing the CSL airbox sucks the most. 

For peace of mind alone, it's worth. It's a shame such a beautiful piece is now hidden away.