there is something up but I dont know what. When i down shift or slow down my check engine light flashes, and my muffler starts to sputter. I changed the spark plugs but it still does this. There was a short period of time (about a week and a half) where the hose that connects to the mid pipe (I forget what its called) was exposed. I guess It could have caused a air leak or sumthing. Anybody have any ideas? Get back at me.

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I have an idea..post the year of car..s4 or s5?
you talking about the split air pipe?the one that goes from the cat to the engine?

 

Sorry bout that. It is a 90 NA. and it is the split air pipe, thanks.

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