In reply to mseyunni:
Try this link Parameterized Classes, Static Members and the Factory Macros - Verification Horizons for more explanation.
There’s really no difference between how all this works with parameterized class or unparameterized classes. You just have to remember that every unique specialization of parameters of a class becomes a unique class type. So your second factory registration macro should be
`uvm_component_param_utils(asnc_ivc_coverage_extended#(T))
This only would be a problem if you tried to use asnc_ivc_coverage_extended with a type other than asnc_ivc_item.
I would also need to see how you call create() on this class. Is it parameterized correctly?
One last thing, are you calling set_inst_override_by_type from your top-level test? if so, just use set_inst_override_by_type() without the factory. prefix.