I own a 2000 Volvo S40 1.9t. I fabricated my own SRI system and had two questions about that and my stock exhaust. The bottom of the stock air hose there is a second plug in for another sensor. I didn't really know what it was for and I knew that I had to of needed it. I cut the stock hose where the sensor is and attached my piping from that on. The stock hose sits still on the turbo like it always did theres just piping about an inch after the turbo just after the sensor. I couldn't take the sensor out so i had to leave it where it was in order to keep the sensor. My question for that is this.

What is that sensor for. Is there another sensor that would plug in like the stock one and be able to fit inside the piping so I can get rid of the airhose completely?

Second Question regarding my exhaust.

The cat converter is apparently clogged as the dealership is saying but were charging me 1200 dollars to replace it. Which to them is the whole downpipe. Can i just cut it out and replace it with a aftermarket high flow cat?? I really don't have the money to replace it and I want my check engjine light off. It failed for emissions could it be anything else but the cat??

 

the sensor might be another 02 sensor. They'er all over these cars. And yes, you should be able to buy an aftermarket cat and replace it, unless there's any other issues.

 

Don't know about your first question, but as for the cat (at least with S60's) it is part of the downpipe and its one piece. You would have to cut the cat off, and weld on a new cat to the old downpipe.