First: A shout out to Wes of the old Bimmerhelp website who made the original DIY and JamesM3M5 who is a forum member. The DIY can be found as a PDF at the end of this post.
[EDIT]
May 2024: Bimmerhelp website is going down.[/EDIT]
August 2014:
I noticed about 10k miles ago that the car wasn't running as fast as it did when new and I had been getting "silent" limp modes (no codes thrown). After reading this thread
http://www.e90post.com/forums/showthread.php?t=726481 I was motivated to do a walnut blast. Good thing I did. The "after" car is like driving the car new. Butt dyno says 40hp and I don't think I am exaggerating. The cleaning was tedious: walnut blast, soak with carb cleaner, scrub and now repeat about 3 times, now repeat for the other 5 cylinders! Cylinders 4, 5, and 6 were pretty bad, especially #5, where some of the sludge was 4mm thick. It drastically affected air flow.
You owe it to yourself to get this done if your car has 45k+ miles without a walnut intake cleaning!
The cool side of the N54 (with the black electronics hub - what the DIY calls the "evil box" - at bottom center):
Detail of the bottom of the intake manifold. I had a bitch of a time detaching the "evil box" (which is just an electrical hub of connections) from the manifold. (Edit:
Be sure to detach this hub off the manifold before you take the manifold off the head!) You can see that I very mildly sanded the edges of the top of the lips on the two tabs so it won't be such a bitch to take the hub off it next time.
Throttle body, which I had to clean as well.
This is the actual top of the throttle body (after cleaning - sorry forgot to take pic of it dirty)
Cyl #1 intake
Cyl #5 intake - gross!
Cyle #4 with a couple blow-suck cycles, pretty clean but I gave it another blow suck
.
15 Amp switch from AutoZone with wire and alligator clips. I was too lazy to jack up the car because I don't think you can turn the crank bolt from top. Edit: If you have an oil cooler you can't because there are too many hoses in the way, if you don't have an oil cooler, you can. If you take off the electric fan and its shroud - which slides up, you can get to the crank from the bottom of the car. Having a lift would make it easy. Important: For those 6MT DIYers who are about to rock, don't forget to put tranny in neutral!
Broken vacuum adapter after 4 cylinders while wiggling it out (thankfully duct tape worked for the final 2 cylinders). Wes is sending me a new one though! Thanks man!
One final note about the sand blaster kit: after getting the "40lb" pressurized sand blaster kit from Harbor Freight (i.e. the "red" media blaster kit), I found it was using waaaaay too much walnut media and I stopped using it and got the smaller "gray" portable kit that is mentioned in the original DIY link above and here:
https://www.harborfreight.com/portab...kit-37025.html (kit also comes with a gun). The portable one works by pulling walnut media simply by pressure drop/bernoulli's principle of the pressurized air flow from your air compressor. I also used the "fine" walnut media which is also mentioned in the DIY.