Well, dude, you can play 100 maps to find no E, and the 101 game, you find 2 E parts. It's a very low chance and then it's random for all 15 E parts you can get from that map. I suggest you to grind the map lv 61 and you will succed in the end.
EDIT : For the second question : 121 Map have more barrels, so more chances for reds than ... idk, another E map.