If you have a ultrasonic cleaner or know someone who does nearby then I’d give cleaning it a go first. The jetting pattern on modern CR diesel injectors are tiny and prone to getting screwed up so be carful cleaning them. But it won’t make it any worse if it costs you nothing/penny’s then give it a bash! Worst happens you have to get a new/recon one anyway.

I’ve got a cheap Chinese ultrasonic cleaner, was something like £40 off eBay and works a treat for carbs and the injectors off my 535d. But my injectors were working and I just gave them a blast while I had them out. Tbf the ultrasonic did a great job, I just used vinegar/water with some baking soda and it worked a treat.

As for while your in there jobs I would get a intake gasket set and do then while your there as they harden up over the years. They are quite cheap anyway.

Change the glow plugs if you think they need doing. But use a tourqe wrench in reverse as if they don’t move after the specified tourqe just leave them be (they have a habit of shearing off) I managed to change 5/6 on the X5.

I would replace the injector seals while your in there but that’s a matter of course with new ones. But if you do clean and refit the old one just get some new ones.

Last inspect all the vacuum tubing under the manifold if it looks anything other than new just replace it while the manifold is off. I always replace mine with black silicon as it’s material properties are way better than the OE rubber hoses.

Your biggest pain will be getting the bloody thing out. It’s a case of roll the dice and pray that they come out easy! I got 5/6 out easy on the e61 and the last one I ended up with the bonnet off and me on standing on the engine squatting a slide hammer for about an hour!

And don’t look on YouTube! Some people have had managed to lift the car by an injector!!!

__________________
E53 3.0d Sport 119,000 Miles
E61 535d Estate - Hybrid turbos and Dark-side intercooler...389hp,792nm