Problems with my 2001 Dodge and Bosch O2 Sensors, pre-cat: Replaced at 160000km (as recommended) with Bosch. For 2-3 weeks, regularly experienced misfire, backfire, hesitation, lack of power until sensors were completely heated up by exhaust (first 5-7 minutes of driving from cold/warmish engine). Check Engine Light never came on and no codes set. Plugs, rotor and cap were replaced (all Mopar) IAC was cleaned too (sensor safe spray). Replaced with 2 NTK O2's and the truck runs perfectly Just as it did before Bosch pre-cat sensors (maybe better?).