ok i have a 92 z28 with a 5.7L in it well a while back it started having a really rough idle and when i would just be cruising down the highway at one certain rpm range it would start surging or whatever you call it and its not any specific rpm range just when its held constant at any of them below say 3500 well i changed the cap and rotor and it seemed like it fixed it well bout a week later it destroyed the cap and rotor.. so since it seemed like the bushing in the distributer was bad causing the 2 to come into contact i replaced the whole distributer.. well i set the timing and everything correctly and double and triple checked firing order plug wires base timing.. well since it had been sitting for a bit i took it out and it ran great no backfire on decel no surging at all well bout 2 minutes down the road it starts it all back up again except its worse almost dies at idle major loss of power worse than befor.. the only code its ever shown was the infamous EGR.. SO any help or suggestions would be greatly appreciated!!

 

check you MAF sensor and relays.