Why does my 1995 Mustang Rev high and then stall out when I start it?

When I start my Mustang It revs high to about 2000rpm and then when it goes back down it stalls out. It usually will stay running by the second time I start it or I can give a little gas it will stay running. But it alway stall on the first start. The person I bought it from said it was the TPS sensor and there was a new one in the trunk so I replaced that and it was OK for about a day and then went back to it's normal routine. Also when I am driving sometimes it doesn't seem to know how much gas I am giving it. If I need to pull out and I give it some gas it hesitates and then eventually it will get a burst of energy and lunge forward.