In order to counter threats like PlasmaKlang, as well as Donphan, two of this deck's biggest weaknesses, and to improve your MMan deck, I find Tornadus LTR(?) to be effective. With a Muscle Band attached, and if your hand has the same number of cards as opponent, the result will be 120+20=140, and since 140 is the PlasmaKlang minimum KO number, bye-bye, PlasmaKlang, and hello, EX defense breach! However, in terms of your deck, I recommend replacing one out of your 3 Manectric-EXes, all your non-EX Yveltals(the ones w/ Oblivion Wing), 1 out of your 4 Muscle Bands and 1 out of 3 Head Ringers w/ 2 Darkrai EXes(for free retreat for those that have Darkness energy attached), 2 Tornadus(the one that has an attack that can do 120 if your opponent's cards are the same in number as yours at the time of Tornadus's attack), and 2 Max Potions. Do you think that's more efficient than having to take a chance that could make your next turn attack-less on the flip, and in case you hope you survive to see that attack-less turn, do you think that free retreat of any form, if only as long as Darkrai-EX is still in play, is better than having to discard energy in order to attack after an unlucky flip that could give your opponent a chance to set up by using hypnotoxic laser+bench-sitting Dragalge or other retreat-blocking moves to ensure that you cannot do anything in terms of damage when it's your turn again?
^ Speaking of Max Potions, in case you think VS. Seeker is enough to get a critical card out of discard, how about ditching Dowsing for 1 Lysandre's Trump Card to draw the max potions, along with the rest of your discards, back into deck from discard, even if it means the opponent has to do the same as a result... You can even replace 1 out of your 3 VS Seekers w/ Startling Megaphone to accommodate Trump w/ a way to undo Garbotoxin should it pop up, knowing that Trump Card is a good enough pseudo-Ace Spec for the new TCG era, and speaking of new eras, it could be the only Ace-Spec-level card (although technically not an Ace Spec) to still be in rotation come next rotation cycle, when I expect the rest of BW's card series to be rotated out, due to the fact that LTR, a Japanese-and-NA-exclusive expansion(Europe skipped LTR and moved on to the XY card series after Plasma Blast in release order terms), is unavailable outside Eastern Asia and North America, surely, they likely will rotate the rest of BW and disregard LTR and the XY Starter Set as a possible base expansion for the 2015-16 Play! Pokemon season... But as there's no other non-electric and non-dark pokemon available that can deal enough to OHKO PlasmaKlang and not give the opponent time to retreat PlamsaKlang and OHKO you with another Steel w/ PlasmaKlang still in play, if you want a PlasmaKlang counter in your deck Tornadus will have to do for now...