The test pipe (which replaces the cat) is available separately from ForcedFed, this is what I am currently using but I did get the cat as well. With the cat, your chances of a CEL go down but the nature of a high flow cat is that it typically has less cells than the OEM and may still not be within the parameters the ECU expects. Reading about user installs here it seems some have had CELs and some not.mark.r said:Understood. But, what I am confused about is, are you using something different than what was purchased with header. Your test pipe looks different than the cat I have with my street heard if I recall correctly. I am trying to avoid the CEL without further work other than the install.
The mechanical CEL eliminator I used has worked for others (also a DIY here about how to use spark plug arrestors for a similar function). I have not yet tried the cat so I don't know if you will have a CEL or not, worst case is that at some point you get the cat error and do the spark plug arrestor mod for $5. If that doesn't work the O2 sim is easy enough to install and only cost $35. I also went ahead and bought an OBDII scanner for $50 just to have in the trunk to read/clear codes.
FWIW, I installed a header on my Lexus and that header was shipped with an O2 sim, when installed I never had a CEL on that car.