I bought my first direct injected engine in a 35k mile Audi S5 4.2. Reading the Audi forums caused me to think that my cold start stumbling might be due to gunked up intake valves. Cuz I'm me, I bought a set of intake gaskets, a media blaster, and 25 lb of crushed walnut shells to deal with it. I drilled a hole in a shop vac attachment so I could suck up the shells as I blasted them. So far the project is going well.

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