silverato with 4.3,A/T, 71K miles truck always starts, but occasionally will not contineu to run.try to restart and it does the same thing no matter hot or cold. it will not continue to run mo matter how many times i try it. if i let it set for 20 minutes it will start and run normally.i have had this problem for about 5 years, and it doesn't seem to get better or worse. it may be several months between problems. i have replaced dist. cap, rotor, plugs, wires,and the oil press. sender.i have no idea what to do next. i am hoping some one can help me. thanks in advance. cat man