Changing the value of capacitor
I guess that you are thinking that bigger is better.Remember that real caps have a self resonant frequency that can be represented by the cap and an inductor in series .The inductance is the total of the leads and the PCB traces.When you put your big 4 microfarad in place of the 1 microfarad the parasitic inductance wont change much .This Quadrupling of C whilst leaving L will halve the self resonant frequency of the system.Your risk here is that your EMC plot will be worse at the high end .Even if you are better at the low end it could still mean a FAIL.