Rough idle loss of power under load

I have a 1995 Chevy S-10 4.3 liter vortec 2wd automatic TBI, vin code "Z" 215K miles, running rough at idle, but has a steady purr while being held at 2500 rpm in park, put it in drive and stomp the pedal it falls on its face sputtering, spitting, an occasional backfire, a nice rich gas smell out of the exhaust. Cannot hold any speeds steadily on the road. The RPM gauge goes irattic and jumps up and down, occasionally returning to normal, Had not thrown any codes / check engine lights. Untill i replaced the EGR valve which i was convinced after speaking with many people (some mechanics) went through 3 EGR valves before getting the right one (thank you delphi), she ran at idle decent for 15 or so mins. then the check engine light came on. so i went to have it scanned and the OBD II kept telling me link error, so another scanner was used with the same results. This truck has new Ac Delco, plugs, wires, cap, and rotor within the last oil change, The light goes off and on now, with no real difference in the way it runs. Any help would be much apprieciated. Rteas48183@comcast.net