I heard the US RSX has a wideband oxygen sensor. True?
Yes it has (although it only reads down to 11.48 AF). This is terrific if you ant to use datalogging to adjust your air-fuel ratios. However, note that not all K20 -Series engines have the wideband sensor. Those that have one are the US RSX Type-S, the US RSX base, the JDM ITR, the JDM Civic Type R. Sadly, those that don’t include the Euro Civic Type R.