1) Use the nodecomposition option which is available in th_autocovarianc...

...es.m: I have experienced that for large models with the HP filter option, this may spare a lot of time, if only the unconditional moments are needed on output;

2) theoretical moments should be displayed even when M_.exo_nbr=1. So, change the logic for displaying the table for theoretical moments w.r.t. tables for decompositions.