Everyone has their own motivations, preconceptions and opinions as to why they do what they do to their own car. That’s what makes the modding experience great and it also provides a market for multiple vendors.
I will say from my experience (if I actually had them – which I don’t of course) that adding DPs will be the single biggest noticeable engine mod you can add outside of software. The turbo spool up response is noticeably quicker and the top end 'choke out' our engines experience is notably decreased. I assume there is some power gained too but I don't feel any mods before software add enough power to make 'that much' of a difference. You can definitely feel the difference in how quickly the turbo spools up with catless DPs.
Also, catless DPs with catless center section along with a free flowing intake makes great sounds without any drone that I’ve noticed. It’s by no means TOO loud and I’ve gotten lots of compliments. You can hear the motor a lot better now and there are all kinds of cool turbo spool up noises. This is in combination with the factory axle back mufflers. If you already have a free flowing axle back then adding catless DPs may very well become too loud.
With regards to the smell. I notice it when I pull into the garage but that’s really about it. I’ve never had issue with windows down driving and smell. I suppose if you are at a dead stop and windows down and wind is blowing at the perfect angle and you are reving the engine then you could get some exhaust smell but it’s never happened to me.
With regards to post cat O2 sensor. The BMS O2 simulator takes about 20 minutes to install and works perfect. As long as you don’t get an actual sniff test at State inspection it will never be an issue. All they do is plug into OBD II and scan for codes. Just as an aside to this, I am pretty certain a couple 2” O2 spacers would work just as well. I’ve had luck with them on other cars and they are used almost universally in the ricer scene. Someone could try them out if so inclined.
Someone said you might get in trouble with the police if you get pulled over. Never in all my life have I heard of someone getting pulled over and that turning into getting the car on a lift to see if it's equipped with cats. That's just way to far fetched. You should have your vehicle shut off long before the cop gets out of his car and reaches you anyways..
I just came across this post I made a year ago. Since people are still reading this stuff I figure I better update. I can not recommend the BMS O2 simulator as a long term solution. After speaking with Terry and others I've discovered that over time this will throw the fuel trims out of sinc. This is really just supposed to be a temporary solution (ie get you past emissions testing then take it off). After several months on the car the pre cat sensors will use the post cat sensor signal to recalibrate itself. Since the post cat signal is faked it ends up slowly getting things out of whack. So, I recommend installing for emissions testing, then removing. After that live with the service engine light or go with an after market tune solution to fix the issue. Mechanical O2 spacers would probably work too but I haven't gotten around to trying it.
Last edited by robertm; 01-07-2014 at 02:24 PM.