77 280Z Boggs Out

I have a 77 280Z. I have replaced the fuel pump, injectors, coil, plugs, wires, fuel filters, distributor cap, rotter button, and the brain. The car starts and runs great for a few minutes, the it boggs out like it is only running on three cylinders. Then in a few more minutes it starts running well agian. I am at my wits end with this car. Any help that can be offered would be wonderful. The only problem is I like it to much to shot it.... :~) HA..HA..