Two shots fired yesterday in the 2900 block of 22^nd Street are believed to be connected.  Port Huron police continue to investigate reports of four black men coming to the door of a 22nd Street home about 12:15 p.m. Sunday; an argument of money ensued; the man living at the home shut the door on the visitors and told police he heard a single gunshot fired as they left.  Later in the evening, the same Port Huron man told police he was approached by a black man about 7:30 p.m. who made threats towards him for calling police on the afternoon incident.  The victim said another shot was fired after he was threatened