1990 lumina igintion???

hello I am having an frustrating problem with a 1990 3.1 apv when engine is started it runs smooth ...if you start driving down the road after aprox 2-3 miles of driving it back fires and is missing intermittenley with a very noticeable loss of power if you turn off the igintion and restart it will go away but 2-3 miles down the road it starts all over again ....I did have a check engine light and the code was 43 electronic spark control (knock sensor)
that has been replaced.....plugs wires and dist cap roter were replaced a few months ago ....in the hayns manual I am reading it says that this sensor if faulty will not adv or retard the engine under load correctly .....could this be causing my problem ?......it also goes on to say that a bad ecm may be to blame in conjuction with the sensor ....but I am hesatent to blame the ecm just yet ...what do you guys think ? currently am testing other possible sensors but unsure whare to go next

no one has any ideas? or was this answered in an eariler thread

Lots of possibilites here, is this a distr. equipped engine or DIS?

distrib eqquiped