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Discussion Starter · #1 ·
What would you do first I'm looking at an ATR downpipe and high flow cat or BORLA cat back. I'm thinking of one or the other. The reason I'm want the atr downpipe as opposed to others is that I want my cats, I live in CA therefore need them and don't feel like keeping my stock exhaust and swaping it in every time smog comes around.

Also has anyone here passed CA emissions with gutted precats? I'd hate to go through all of the work of gutting them then have to buy some used ones from a scrap yard.

Right now my car is moreless stock just open air k&n style filter... mbc and turbo timer will be installed this weekend. The turbo timer has a boost meter w/peak hold. Blitz DCII DTT. So which upgrade would be more benificial. I'm thinking that the catback would be more for sound than anything else... so are there any noticable gains from a dp?
 

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ATR downpipe should definately be the first of the two if your lookin for $ to HP rating. THe stock DP is VERY restrictive, much more so than the stock cat-back. I've read that the stock cat-back is not really required until around the 500HP mark. DP should be good for a 18 to 25 HP increase as soon as you bolt it up:) The same cannot be said for the cat-back.

If your going for sound alone than go w/ the cat back. Keep in mind though that your stock exhaust will sound deeper after installing the DP, so even if you got the DP it would improve the sound.
 

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Well said,

I have to agree with jdc4085. Besides my boost controller my downpipe was the best performance upgrade . It is the best bang for the buck and gives the best seat of the pants performance feel. Definately go with the D.P.
 

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If you want power, go for the downpipe before catback. If you want sound go for the catback. It all depends on your preference.
 

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I already have the Borla exhaust, but I'll be getting the Stillen DP. I don't if I will be gutting my rear cat because of emissions in Cali.
 

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The stillen DP is awesome, but it has a tag on it Not for Highway use, Offroad use only, I'd think this would be difficult to get by CA inspectors. Therefore I'd probably go for the borla exhaust and a DP with the hi flow cat or one that doesn't eliminate the cats but uses a test pipe.

I've got the stillen and the borla and would estimate the power gain at around 40hp for both mods. (30 for DP, 10 for catback)

But the stillen DP and keeping the factory exhaust sounds pretty good all by itelf. Opens the upper end up nicely.

LW
 

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there is a group buy going on for the stillen DP right now. Price is at $315 and dropping.....check out the group buys section.
 

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WannaBeRT said:
I just posted a new subject on this... :( but will no precats/ high flow main cat be able to pass emissions?
Probably not in Cali.
 

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I passed smog in Ca with a pitroad cat-back minus one pre-cat, but just BARELY. I also ran a bottle of that Pass or Don't pay stuff first. I think that might have been the difference actually since it was so close on the idle reading. The 2k rpm test was easy, but it's the idle one that almost got me. If I had a DP or had I gutted the other precat I doubt I could have passed no matter what.
 

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Grandpa
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I run an ATR downpipe, test pipe, thru the stock back end. Definately made a nice increase in power, spooled a bit faster as well.

As soon as I have the money, I plan on doing the cat-back as well.

But, it sounds like your in my boat, only can afford one at the moment. I don't think you'll be dissapointed with the DP. Gives you a bit better tone also!
 

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Discussion Starter · #13 ·
So gutting the precats may effect my emissions at idle?

Well I think that I"m going to go with the down pipe and keep my precats. I wish pre-cat eliminators weren't so much $$$
 

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Grandpa
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I passed illinois emissions with a ATR DP, ATR high flow cat, and Gutted pre-cats. They are pretty strict here too.
 

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I think you could pass inspection if you bought the stillen pipe and gutted the rear precat, but changed the downpipe back to the stock one before getting tested. With one precat and the main cat to handle emissions you'd probably do fine. Dropping the downpipe and swapping it really isn't hard and only takes about a half hour if the bolts aren't stuck.

LW
 

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I had a Borla cat back first,then got an atr dp-was installed today going go to pick tomorrow. Hope its as fine as everybody says it will be. My mechanic is a little bit concerned about flexing. The stock dp has two braided sections but my new dp is straighr thru. Anybody hear of any probs with this? also,he had to cut and reroute the dp because it it didnt match up exactly with th borla system ( I had him remove the cat).I checked with borla and they said they didnt have a dp available so what do you do?
 

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If you do a search, there has been some talk recently about busted pipes on a specific downpipe. I can't remember the maker of the pipe but it was one of those without a flex section. You can have a flex section added but I think that would compromise the efficiency of the dp...I think, and its conjecture only. The stillen dp has a flex section where the main cat usually sits and easily mates up with the borla.
 

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Its the DN Performance DP that has been breaking. This means that for quality and service DN is 0 for 2 :D (see group buy from DN performance for details)
 

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i was thinking of getting the melton downpipe
Great thought. I picked one up a few weeks ago, what a difference! Easy to install too.

I opted for the 1st revision styling. Looks like it would flow better than the 2nd revision. I'm not sure if he's still selling them though, seems to sell them on group buys only. You might wanna PM him and ask.
 
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