Theft Light Coming On

I have a 2000 gt 4.6 5 speed starts every time but when u start to drive it u will make it a few miles from home and it will start to run like it's running out of fuel and the security light comes on then u can pull the battery terminal off for about 5 minutes and it will got about 100 yards running good then do the same thing
I'm sure this has been talked about a lot but I've been searching but can't seem to find anything but dead ends if anyone could help would greatly appreciated

If I don't have a tuner is it to late to buy one and turn it off what brand can I get to turn it off