Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
It coult be EGR related, and one way to test for that, is to take a soda can and make a gasket for it. Just trace around the outside of the valve and cut it out. Cut out the bolt holes and a hole for the pintle, but do not cut out a hole for the other passage. Put it back together and if the problem persists, its not the EGR valve.
If not the valve, then you need to look closely at the fuel system. These systems need about 12-13 PSI and when the pumps get old, they might put out 8-10 which can cause minor issues. Also, between the pump and the sending unit, there is a short rubber hose that likes to split, or if it has a pulsation dampner instead, sometimes they don't seal right and can be replaced by a short section of fuel hose.
One other thing to look at is the distributor. Remove the distributor cap and look at the toothed wheel underneath. If there are any cracks in it, or the coil around it, it will need to be repaired.
Hope this helps, and feel free to ask more questions if needed.