my car is knocking after the repairs are done

First of all, my car was broken on the freeway  and take the car to service shop and
they want to charge me $350.00 just for diagnosis and I refuse get a town at home.  
one my friends scan the car  and shows 2 misfire 3&4 .then I think is time to do the
service we replace the spark plugs and check coils , wires, oxygen sensors 2 new
ones. and later shows poor mix fuel and air.we replace regulator, filter still the pump the
oil change did before now don't shows any code and the oil light appearance on the
dash. give me your opinion please I appreciate too much . I am thinking can be the oil
pressure switch.