-1 Necropotence
Don't cut Necro; the card draw is insanely broken, especially when running multiple Tendrils, since even if you can't win outright you can always Tendrils to refuel for next turn. Necro gives you the most cards for the least converted mana cost.
The artifact utility cards, such as Neddle and Explosives, are not good in a combo deck. Your goal should not be to destroy or disable problem permanents, but to actually win. As such, bounce spells are the best way of dealing with board-based hate in combo, since they are the most efficient. So, if you are worried about stuff like that, add 1-2 more maindeck Chain of Vapor, since it deals with everything and can actually build storm and mana when going off.
Adding wheel as suggested is possible, but I would rather run Tinker/Jar ahead of Wheel since it is less risky, and I wouldn't bother splashing for Wheel unless already playing Twister. Playing all the draw 7s is certainly a valid option, which results in a different deck than the list I suggested--since you have more early bombs, you can cut the Confidants and just focus on early game instead of possible long term incremental advantage. The problem with this approach is that draw 7s are not very strong without full power. In an unpowered list, I would definitely stick with the Confidant/Nauseam plan.
Regarding Pact of Negation: The problem with Pact is that it is hit or miss. I tested and played with Pacts for a while, and they are either amazing in allowing protected turn 1/2 wins, or they simply sit in your hand while you lose. Eventually I cut them for Thoughtseizes and never looked back. Thoughtseize can not only clear the way for all your bombs, but also actually disrupt your opponent, which is often critical in winning against Control, other Combo decks, and even Aggro like Fish or BGW.
Look at it this way; Pact only really useful when you have an Ad Naseam or Will/Bargain in hand and enough mana to cast it (at least 5)--and even under these circumstances it is only good against decks with Force of Will. Thoughtseize is good whenever your opponent has a hand and you have 1 black mana. Not to mention the fact that you risk losing to Pact if your opponent has double Fow or something, whereas with Thoughtseize you can still have a chance to win depending on how it plays out.