2004 land rover discovery 4.6 engine with secondary air system how do i tell if mine has it or not?

Probably the best way/easiest. Is to look under the hood for the emission label. should be mounted in the center of the front support near the hood latch.

If it says built to California emmison standard it will have the 2nd air system. Might also have it stated on the label. not sure.

If it says built to federal emmsion standard's it will most likely not have 2nd air system but not always the case.