So i've managed to fail this years emissions, even with my stock DP back on. Apparently my NOx levels are through the roof. Is there a cost effective and/or quick fix for the problem that Doesn't involve retuning? If need i can post more information. 2004 WRX

 

Sounds like you have a bad cat. Are you running the stock catted exhaust also?

 

Just the downpipe, my uppipe and exhaust are both cattless. I'm also boosting 18lbs. right now.

 

The boost wont matter. I bet your cat is bad in your dp and since you have no other cats in place your getting high readings. I would try swapping the dp to another stocker or putting your stock exhaust on and testing. If you want to play it safe, do both. Make sure you drive your car a bit afterwards so the cats can get good and hot to filter correctly before taking it in.

 

I'll try throwing the entire old exhaust on, the only worries i have is that i'll have to put the old uppipe back on. That doesn't sound fun to me.

 

Yeh, you wont need to put on your uppipe. Usually all you need is your stock downpipe, but it doesnt sound like yours is filtering correctly. I keep my dp connected to my stock exhaust and just install the whole unit each time in one piece just to be safe. It doesnt really add much more time since you only have to worry about the dp to turbo bolts and hooking up the hangers for the exhaust when its all together. It just takes an extra set of hands usually to lift it all.