I STILL HAVE THIS CODE 0421 and 0171 TOO. OBX HEADER WITH NON FOULER, WEAPON-R SRI (WITH TOYOTA MAF SENSOR), NGK WIRES AND COILS BOOTS, NKG SPARK PLUGS DBL PLATINUM!! I DONT KNOW WHAT ELSE TO DO!!! PROBABLY IF I PUT A BOMB INSIDE THE TANK GAS IT MIGHT SOLVE THE PROBLEM!!