Do you still have the original Delphi wires in it? Mine did that after I changed the wires and plugs. I used Bosh wires and auto lite plugs and the problem started. I got myself a new set of delphi wires and it fixed it. Take a look at it at night ans see if you can see any blue sparks from the wires. You can control the throttle by hand to push the rpm's up and see if it is shorting out somewhere. "like when you take off from a stop"