2001 chevy impala has a P0420 code and a check engine light that will not reset. Earlier P-codes indicated a problem with cylinders 1-3. these codes reset after a while. Found intake vacuum house off on top of the engine, put it back in place but boot is split. Could this cause this problem?

Thank you, The code also indicated Bank 1 whatever that means.

Where would the engine coolant temperature sensor be? How would I know if there is damage to the exhaust pipe retarded spark timing?? Which O2 sensor is malfunctioning?? I have been told the the catalytic converter appears new and in good shape. I have noticed a smell like burning plastic comping from underneath the vehicle. I was told by Chevy that this is common and not a malfunction. Thank you, The code also indicated Bank 1 whatever that means.
Where would the engine coolant temperature sensor be? How would I know if there is damage to the exhaust pipe retarded spark timing?? Which O2 sensor is malfunctioning?? I have been told the the catalytic converter appears new and in good shape. I have noticed a smell like burning plastic comping from underneath the vehicle. I was told by Chevy that this is common and not a malfunction.