Here’s the mystery…when driving on long, level roads at a steady speed my K2500 Suburban w/6.0L engine will sometimes suddenly “semi-stall” by dropping engine speed to ~1000RPMs, no throttle response at all until speed drops about 10 MPH, then picks back up and runs/accelerates normally. If only traveling at about 30MPH or less (i.e. slowing down at a light) it will sometimes just die completely, but shifting to neutral and restarting gets it back to normal. A little history…132K mileage, on its 3rd fuel pump, new plugs & wires, check engine light only came on one time, with P1516 code and reduced power msg. My mechanic checked and reset and sent me to Chev. Dealer to update software…problem persisted without any codes or check engine, replaced throttle body. Problem persists whether cruise control or towing mode or speeds from 60 to 20…if at a steady speed. No problem if accelerating or idling. Any fresh ideas?