Xsara 2.0 100kW random cylinder misfire

[stefaxsara20]

I had check engine light on, read it with diagnostics and got P0300 Multiple/Random cylinder misfire and P0410 Secondary Air Injection System, i changed sparkplugs just to be sure they are not the problem because they were not changed for some time. Car starts normally, but is experiencing rough idle all the way up to 1500rpm, where shaking stops. Does anyone know if secondary air injection pump can cause a misfire, and where is it located. Thanks in advice. The car is '03 Citroen Xsara with 2.0 16v EW10J4 RFN engine

[wheeler]

The secondary air pump is just there to heat the catalyst up faster.
Coil pack failing would be the most likely culprit.