@ Steve
Since you are not running Burning Wish anymore, could you explain how this would effect your sideboard? I, for one, don't see much use for a 'boarded Hull Breach if you cannot fetch it with wish. Also, Balance would seem out of place as well, given it's relatively narrow usefulness for the deck and because of the W in the CC. (Or am I missing some tech use for Balance in some match-up or other?)
My guess would be to start with:
4 Xantid Swarm
3 Hurkyl's Recall
2-3 Chain of Vapor
2-3 Oxidize
But what next? I've been looking for good sideboard cards, but can't seem to come up with something worthwile. I've considered Naturalize and Echoing Truth, but neither of those seem to solve anything that cannot otherwise be solved by Hurkyl's Recall or Chain of Vapor. There must be something I'm overlooking, as I cannot imagine having to fill the SB with a handful of cards one rarely uses.
Perhaps a small description of my meta would be useful. Basically it's pretty random, the only viable decks I don't see played much are other Tendrils-based combo-decks, Tog, FCG, TnT and Workshop-slaver (I do face Workshop-Prison reasonably frequently, though). I also face freaky old deck concepts like SuiBlack from time to time.
Any comments would be greatly appreciated. Thanks to anyone who cared enough to read this post.

Greetz,
Remco