My fix for: evap leak ; misfire on all cylinders ; both bays too lean

[Ghostkjb]

Symptoms I had in order:

evap leak codes
wanting to die on idle
misfire on all cylinders codes
both bays too lean codes

Parts I replaced in order:
Air intake boot: https://www.amazon.com/gp/product/B00FFV17U6/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
I replaced this because it commonly cracks and tears causing similar issues. Mine was in bad shape.

I was researching replacing the idle control valve on this video, and it informed me that the box that I thought was electronics, that happened to have the small hissing sound was the Air Intake Manifold Valve
I replaced both at the same time. HUGE thank you to this video: https://www.youtube.com/watch?v=AgMFHaRhRdI&t=14s

Idle control valve: https://www.carparts.com/details/BMW/Z4/Replacement/Idle_Control_Valve/2004/3-dot-0i/6_Cyl_3-dot-0L/REPB313213.html
Air Intake Manifold Flap: https://www.amazon.com/gp/product/B07GBTTTSV/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Replacing these last two parts fixed it for me. I'm VERY confident it was my Air Intake Manifold Flap. It was in ROUGH condition.
The boot is a common issue too due to tearing and cracking.

 

[colb]

Glad you sorted it, common problems on the Z4 given the age they are now, rubber parts degrade over time and repeated heat cycles often causing air leaks which in turn fool the exhaust sensors to think its running lean and demand more fuel at the injectors to richen the mixture. The fuel trims then remain high resulting in rough running and a decrease in the mpg you get, more visits to the fuel station is an attention getter as your wallet suffers. The idle control valve gets sticky over time and can be cleaned out if you take it off and spray carb cleaner in it to wash it out. Once clean if you shake it in your hand you should feel and hear the internals rattle as it moves around when its freed up. The Air Intake Manifold Flap is called the Disa valve that shortens the intake path when it operates, always good to pull that and inspect its condition, some models have been known to fall apart internally and bits get sucked into the engine with dire results, not sure which model had this problem but checking condition will never hurt. Just ensure it seals ok when its put back in. If you hear a clacking sound comming from it with the engine running its a sure sign that it needs replacing. BMW engine do require a sealed CCV system to run right so all the hoses rubber and plastic and intake boots need close inspection for splits or holes, replace any that are fond in bad condition.
Some air leaks can be hard to find visually, a smoke test in these cases is a sure way to find any if your handy you can build a smoke tester for home use, loads of Youtube videos on how to do this.