so i just got the code read and it states
po420 and po430 bank 1 bank2 catalyst efficency below threshold.
researched online and that suggests the o2 sensors in my cats. i have stillen HFC. any suggestions as what i should do to get rid of that or why that happened??

 

Look into o2 simulators.

The easy version is that the post cat O2 is looking for XX% lower than the pre cat O2. Your cats are now high flow/clean the air less and it triggers the CEL.

edit: you might try spark plug anti fowlers for the cheapest possible fix.

 

FI offers anti-foulers with their HFCs.
You may want to ping Tony over there. He may be able to help you, even though you went through his money-grubbing, thieving competition for the HFCs..... not that I have any strong feelings on the whole Stillen matter.

 

The antifoulers work. On my STI I had a catless turbo back and never got a check engine light for catalyst inefficiency with the mechanical o2 fix so I'm sure it would work with the HFC's.

 

just messaged stillen and they will send out the anti foulers for my sensors i should have them soon and see if that helps. i didnt get any push back from them or anything just told them about my problem their like ok you get it next week thats it. pretty sweet.

 

Having done a search and not finding the information I needed I PMed my buddy Sean (SXEXCX) about my throwing the "Check Engine Soon" code after installing HFCs. He told me about the Spark Plug Non-Foulers and how they worked. What I found out and thought I'd forward to our members is that the correct size is 18mm and the package number is 42002. And, you're going to need a 1/2" drill to enlarge the small hole for the sensor to pass thru. Hope this helps when you run into the same issue I had....
Gary

 

I've used anti foulers before and they work. Did it on my catless Mitsu Eclipse from way back. Do that and the light will go away.