Ya I know, another downpipe question...... but here it goes.

I have an 04 sti (99k miles) with an SPT intake, nameless catback exhaust and a Cobb AP V2 running Stage-1 91 oct. This is my daily driver and I'm really thinking about going stage-2 but I'm worried about it harming my car.

So that's the first part, here comes part 2.

So I live in Montana and don't really have emission checks, so I could run catless and not have a problem with the problems that come around with checks. A problem that does exist however is that there are no true tuners in my area and I will have to be running the OTS stage-2 map from Cobb. This map is designed for a catted DP and catless causes boostcreep/overbooster. But i have heard you can get away with running catless by using the stage-2 LWG map. Also seen that people have to weld in 02 bungs in the top of their downpipes but some come made like that already (cobb & tanabe).


So what would be the best downpipe for my situation? Catless? Catted? Bellmouth? Divorced?

Thanks in advance

 

I also have a 04 sti, I am running a Titek catless bellmouth DP. I used it w/a OTS stg 2 map before I got my custom tune, without any problems. I believe that the OTS maps are not really compatable with aftermarket intakes unless its a Cobb SF intake. So I would go back to stock there and use a K&N drop in fliter with your stock airbox. An aftermarket intake really has no benefit with your stock turbo anyways, and this in combination with a catless dp may cause an overboost. If you buy a catted DP, Cobb's dp is the way to go. I would run a catless bellmouth dp and run Cobb's AZ/CA 91 oct OTS stg2 map for your car. I would ditch the intake and if you get a CEL for overboost, then use the LWG map which should take care of that. The 06-07 had the worst cases of overboost. If at all possible you should try to find a good subaru tuner that can tune with the Cobb AP. That is the best posssible choice, then you could still use your intake if you really want. I would not worry too much about messing up your car, but since you already have higher mileage, a compression and leakdown test would give you good piece of mind before modding.

 

About the intake, I do not own the original intake/box that came stock with the car so I'm pretty much stuck with the SPT. But I've heard that as far as intakes go, the spt is definitely one of the better ones.

 

The Cobb OTS map is also compatable with the SPT intake.

 

Been looking at the MadDad Essentials Catless Bellmouth downpipe, anyone heard or have any experience with this product?
http://www.daddysscp.com/product_p/mdbell.htm