I would be very very very careful with that cleaner thing... injectors are not intended to be powered by a continuous 12V, but pulsed, if you leave it on long it might burn them up.

I have used Mr. Injector for a few engines in the past and have had great luck, plus you have actual flow rates before and after

https://www.mrinjector.us/

A combination of several brushes, engine parts cleaner, lots and lots of towels, and compressed air :)

And mine doesn't seem to have a huge issue with the valve stem seals just yet, but I know it's right around the corner. 100k miles and 16 years old.... As much as I've taken apart, I've only come across one thing that isn't original: the air struts were replaced with arnott units (and I've removed those and converted to coils). So I'm basically taking the "replace everything" approach.

Agreed, I will only be applying power for a few short bursts. I don't have any reason to believe the injectors have issues at this point. I sent the injectors for my 2002 maxima off for the same service, but it has 260k miles on it... The X5 only has 100k so I'm just doing my due diligence while the injectors are off the car (and replacing the O-rings, of course).

For those in TX or the south, I can vouch for InjectorRX, in Houston. He cleaned and flow checked 8 M62 injectors and the fuel rail I bought on EBay for a reasonable price. I needed to paint the rail so he shipped it un-assembled whereas assembly with new o rings is included.

Replaced the fuel filter - what a PITA! It was the factory original w/ 117K miles on - dated '2005' LOL

almost 100% sure mine is original in the 04..... 215K on it :O
I have one in stock,

They are good for 200-300 but the o-ring in the FPR usually fails first

Yeah that was one of those jobs where I kept saying “why did BMW make this so difficult?!” Getting those stupid fuel lines disconnected had me red in the face. Mine was also original when I replaced it at 100k.

Will fuel line pliers fit in there for removal? I have a set to use. Replacing the fuel filter is on my maintenance list.

I had some as well and tried using them to assist in removing the little clips that hold the fuel lines on, but their position made it really difficult. I think what I ended up doing was using a tiny flat head screw driver to pull the clip/insert out. But even after that clip was removed, those fuel lines took me a while to get moving - I was afraid I was going to break something. I'm guessing it would be way easier if it weren't in an awkward position, and I didn't fully remove the splash shield so that might have made it harder...

I'm pretty sure the fuel line connections changed over the lifecycle of the E53. My fuel hoses snap onto to the fuel filter, and I released them by pushing a blue button at the end of the hose. The PITA part is getting the splash guards off for access to the filter. So many screws. So much dirt in eyes. LOL