99 model v-6 run then dies

My friends chevy v-6 work truck is kicking my tail. It has run fine for the last 3 weeks after replacing the distributor, dist. cap, rotor and GM wires and plugs. All of a sudden its back, at any time it might skip, backfire then cut off. Wait 15 minutes or so and it will crank up like nothings wronge and run great for another 50 miles then start the cutting off process all over. There are no codes at all. I've not changed the coil yet, any Ideas? Thanks