How long does it take for the ECU to learn a new setup? Basically I have put a K&N panel filter into my Vauxhall Astra mk4 1.6 8v (yeah I know, not exactly a fast engine). Since doing this I keep getting the engine management caution light. The thing is it is running superbly. Should I reset the ECU (disconnect battery overnight)? Or see if it learns the new arrangement? Some have said that is can take a few hours for the computer to adapt.