Put a Killer B2 on my 03. Takes a new downpipe and a little tweeking to make it fit right. Spools quick, nearly as fast as the stocker. Seems to flow a lot more air in the 10-20psi range, that's where you feel it most. Less egt's and smoke with a much stronger feel in that range. I'm heard of a few guys having trouble with the killers though, we'll see what they tell you here. Sounds like HTT did well with the customer service on those units though.
-Scott