Sideboard for Rakdos aggro?

Really you're close enough to RDW (Red Deck Wins) that I'm not sure having the black splash helps you all that much. 

Young Pyromancer has the potential to be a sick card, but at current nobody has really figured out whether it's more for control or aggro builds.  On the one hand, the thought of dropping more creatures is nice, but they're not really big enough to do all that much for you without some help.  Even if you consider them as an asset with Hellrider, you could still easily be pumping out 1/1s with Krenko, Mob Boss, Krenko's Command or even Thatcher Revolt.

The question is whether you want to be aggro or a bit more controlling - sadly trying to do both at once isn't typically a good strategy.  By this I mean you'll want more aggressive, haste creatures rather than all that removal (or vice versa).  I'm thinking you might slide the Dreadbores and some of the Doom Blades over to the sideboard and replace them with Rakdos Shred-Freaks or something to that end.

Look around at the different RDW builds and pick and choose what you want to go with... obviously if you're in a Tier 1 populated area, then you'll want to run with a more similar decklist, but if your LGS isn't as full of people just net-decking, then have some fun with it.  Personally, I'm a fan of Sire of Insanity and could see more of a Rakdos/Jund midrange, but that's just me.