Originally Posted by PA-Outback2000
racefacefx... when i said bolt-on i meant that there was no cutting or welding needed. do u have the borla with random tech cat? where is ur answer based?
on a 2006, the header and cats are one unit now, where the older ones, the header and cats were seperate. u need these to be changed at the same time. the dual converter on the random will most likely not throw a CEL. my car didn't throw one with the header. the stromung cat will throw the CEL. if a TWE EL header is added to either, there will be CEL all the time.
I said they are not bolt on because they do not "bolt on" to a factory header for the OP's impreza. So some type of fabrication is needed unless he replaces his headers.
So a more efficient header design that gets much more heat to the cat will cause the cats to be less efficient and throw a code but an inefficient header, will not throw a code? That doesn't make any sense. There will still be a P0420 code even with factory headers and a HFC. the headers have nothing to do with it. The fact that you havn't gotten a code floors me.