Hi Cyrus200.
I use oven cleaner let that soak in because i have spares, but you could just let it do it's thing for an hour before jet washing it out, also scrap out as muck muck as possible before hand.
Here is the manifold and EGR i swapped out yesterday at our meet.
He had a little smoke after driving it off up the road, that would be the engine clearing it's throat/lungs so to speak after having surgery to clear the air ways
when you have your manifold change it can have a bit of a cough before clearing.
I'm not surprised either if your esophagus was full of gunky food like this below
Sean's EGR and manifold.
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Inside the manifold best shot i could get.
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It is supposed to look like this.
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It can also look like this.
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Which ever you prefer mine is the later type.