My blazer sputters when cold and hesitates when accelerating at high speeds (50+mph) sometimes backfires under drivers feet when cold and sputtering

Check the throttle position sensor. tap on it lightly with a screwdriver handle while truck is running to see if there is any change

Your timeimg is off if theres a distuributor there just might be u need to losen the bolt right below the distuributor with car off once loose start car it only needs to be loose enough to turn startcar turn ur tarding it upping the amount of gas and air intake u absoreb turn it to the right ur engine should idle hire dont turn to must at all little by littleas u turn hairturns at a time get dont shut hood alll way get in go down the street punch it if it feels good gets it and goes ur good if not keep repeating prosscess until it feels right to u