oven cleaner works great to remove the buildup.
best ive found was heated organic parts cleaner... let it sit close to a boil.. shake it round.. stuff falls off... no damage to egr rubber so on..
dealers no clean.. my local one tells owner turbo bad.. so they sell for cheap to me.. i clean intake and run like new... what you get for going to dealer... i even asked bout intake 1st.. guy arued w/me that dealer smarter.. so gave him his clams.. built car.. was such a nice car too.. rip.. passat unicorn (price paid/fixed did not exist then.. and still no one sells any tdi at it) will live on though.. just unsure if i selling conversion or using still..
Just some advice for those who use oven cleaner on aluminum parts. Oven cleaner contains Lye or caustic soda, same difference. Don't let it sit over night cause it WILL eat away at the metal. I left an aluminum part in a hot tank with Lye & the next day found a skeleton of the part I put in. Use gloves & glasses, too. It's really nasty stuff. I use a vat of the stuff to clean my 2 stroke pipes down to metal & it works awesome.
The wifes car was so anemic you could barely get up to speed. At first I thought it was the maf sensor but sure enough it was the intake. It was worse than catlin's picture yet it still started and idled perfectly. Luckily the intake ports weren't that bad. I now keep a clean intake on hand to reduce the time it takes to do the job.
ive alawy thought a online shop should core them for more then new price and sell cleaned ones for profit... a vibrating hot tank... throw in.. when removed clean.. the issue is the core... takes my guy 3 days of swooshing the manni in the liquid every few hr when its warm... nice steamy like washing dishes.. some organic cleaner.. no damage to egr.. aluminum pretty.. and no scraping.. he has clean on shelf.. but kinda word of mouth due to core..
hows he know you shipping one back or that say egr rubber not damaged.. some have this.. makes cleaning this way best.. but to have clean one to bolt in place at time of job.. sweet..