Was not correcting you Kev, as I know you know whats what, and like me you must get sick and tired of correcting everyone!

It was for everyone else's attention.

EGR = exhaust gas recirculation, which I believe is for emissions/enviro reasons and does what it says, re-itroduces exhaust gases back into the inlet system.

APS = air pulse system and is used to bring the CAT up to heat quickly, as they only work once hot enough and again is for emission reasons, and it does this by bleeding fresh air into the exhaust manifold, which allows any un-burnt fuel present to combust and generate more heat in the exhaust and heat the CAT quicker. This usually only runs from a cold start up.