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      12-25-2012, 04:03 PM   #14

Drives: 2012 Z4 sDrive35i M Sport 6MT
Join Date: Nov 2010

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Originally Posted by e92driva View Post
Hey guys, i'm looking to buy some DPs but I have a question concerning inspections. In MA, we have to do visual and emissions testing, so if i get catless DPs, how am i supposed to pass inspection?

I did a good amount of searching and the answer is either get the DP fix, or take out the DPs every time for inspection. I also saw that if you use a JB4, it doesn't throw any codes. I'm currently running COBB stg 1 agressive and know that i can clear codes but i don't think it'll pass emissions..

i needz input
The majority of people who end up modding their cars go cattless DPs. If you go cattless you "risk" the following
  • Drone
  • Rasp
  • Smoking (from seals that are about to go due to no back pressure)
  • Not legal ie being busted
  • Will spend more money to have them uninstall/reinstall unless you do it yourself

If you want to stay clear from all the above, get downpipes w/ HighFlow Catts and have your mid catts removed later

Edit: Kinda figured I was going to get a back lash about the DP / Smoke statement on the side lines. So let me clarify.

Usually when people do DPs the next thing that is done are removing mid-pipes (sooner or later). I did not say you "WILL" blow your seals if you go cattless. I said you "RISK" the chance of smoking usually caused by seals coming to their end of life. This mostly happens (smoking) with those who are "completely cattless", which is one of those mod bugs when you start removing catts.

Being cattless but keeping your mid catts retains some sort of back preasure which in return "reduces" the chance of smoking like a chimney. However, you will still fail emissions unless you rig up something like a DP fix . Our turbos were designed to have some sort of back pressure and the seals on them suck azz badly.

My recommendations to the OP was to get downpipes with HighFlow catts and still pass emissions even if he decides to reduce more back pressure by removing the mid catts

Last edited by BQTuning; 12-26-2012 at 11:15 AM.