Is there any reason why putting in a new Bosch O2 sensor would cause hesitation at low RPMs? There was a little hesitation before with the old (OEM original '93 w/ 157k), but now it's worse at low RPMs. Does the ECU take a while to learn the new O2 sensor? It feels like there's a power increase starting abruptly at ~5,000rpms though. I'm going to put the old one back in for testing soon.