Idle & low speed poor running 95 Mazda Millenia

Have a 95 Mazda Millenia - ran ok till plugs, cap & rotor changed - now it will barely idle & hesitates, coughs & spits until you get it up to 3K rpm - there and above it’s smooth - below 3K it loads up & blows out black smoke (rich) Any ideas what’s wrong ?

Check the timing.