been a rough day sir, hell who am i kidding, been a rough year, i need your HELP!!!

i have a 2001 Subaru Outback Limited, with the 2.5 Liter(2458cc) engine in it, it has under 75k on it... i had some crap i had to do today, and was low on gas, put the 4 bucks i had in my pocket at 76, and drove to get some more money, put in 10 (Arco gas which i hate with a passion) for the drive to University Place from South Hill and started on our way, the traffic was insane around the mall trying to get to the freeway, so we meandered downtown and jumped on I5 in Fife i think it was, drove to UP, did my thing and headed home... on the way to the store, i saw that the Check Engine light was on, and freaked the fvck out...

ran to the Schucks, and it is throwing only 1 code, the p0420 Catalyst Efficiency Below Threshold (Bank 1) code, WHAT IS GOING ON??? from what i have gathered, if it was an O2 sensor or Knock Sensor (that i have replaced already), it would be throwing its own code as well as the 0420 code, but its just the lonely 0420 code... car does not run any different, starts right up, no sputters, knocks, pings, spurts, nothing...

if i remember right, it threw the same code when the KS went out, but when i replaced it, it went away, when the KS was failing really, the car would lag, sputter, ect... nothing of the sorts this time, and its only that one code as well...

what is going on Steve?

this is from a forum just for Subaru Outbacks, is this correct? appearently, its from a Tech engineer:


The alleged problem with low converter efficiency that triggers a Check Engine light isn't real. The OBD II system uses exhaust gas oxygen content to gauge converter efficiency. That's like using fuel pressure to monitor fuel flow. The assumption is that a given pressure in a line of a given diameter will flow a specific volume. However, if there's a restriction in the line, volume will be severely limited, in spite of system pressure.
With the OBD II system, the assumption is that oxygen content behind the converter will be substantially more consistent than content in front of the converter. And that's true when you have a restrictive converter that causes exhaust gases to back up in front of it. But when you increase flow capacity, the residual oxygen content behind the converter is not as consistent, so the PCM erroneously thinks converter efficiency has deteriorated. In spite of the fact that the system "thinks" converter efficiency is below the acceptable threshold, the converter is doing its job and the vehicle will pass an emissions test.

website here :

http://www.subaruoutback.org/forums/66-problems-maintenance/3762-obd-ii-code-p0420.html

do i have a huge disaster thats going to royally fvck me? i really could use your insight sir.... and anyone else out there that works on newer cars, your advice is welcomed as well, older cars im ok with, newer cars im not so ok with, i can fix minor things, but couldnt pull and install a motor thats for sure, plus i dont have any money for it, so this is all gonna be done by me, or so i think...