I posted a similar question somewhere inside a thread once, but every few weeks I've thrown a p0420 or p0430 or both. I've gone through 3 pairs of cats trying to fix this. I refuse to believe after 500 miles these cats are clogged or killed. My O2s dont seem out of whack at all, but my STFT is fluctuating in normal range (around 0) but no matter how long my car runs my LTFT stays +10 to +13 which is way too high. Why won't my LTFT drop? What could cause this kind of condition?