Derek, I'm going to go way out on a limb here, and take a very un-educated guess (since I'm no mechanic). But could it be running lean because of the Saskins intake is actually "too" efficient? Also, aren't you running headers too? Wouldn't these two mods alone help create a lean mixture if the cars computer couldn't compensate for the increase air flow?
I'm not defending Powerchip, but I would think it was probably programmed for an otherwise "stock" engine.