help with a 4.3 vortec.
 

hi,new to this site,thanks in advance to anyone who can help me.i have a 2000 express van that died on me. brought it to a shop and they diagnosed problem as a bad spider/fuel meter body.had it changed as well as a tune up done. still have the same problem.here's what the symptoms are .runs fine when cold.after long driving time, aboiut an hour,engine will sputter and lose rpm. when pedal is depressed rpm will come back.engine eventually stalls.will restart but at idle will start surging.put a scanner on it and not reading any codes and parameters look ok.fuel pump relay is clicking in and out which is related to surging.thanks again