I skimmed through the posts, so I appologize if I repeat something.
I ran a 13.8 last year with just an upgraded BPV and a catless test pipe. I had an MBC installed, too, but it wasn't working properly and I was only getting to the stock boost levels. Just lower the tire pressure in the front to 25psi and raise the psi in the rears to 40psi...that will allow for better grip on the launch and less rolling resistance up top. Take out the spare tire, also...it's pretty heavy. Quick slip the clutch to launch...dumping it will just cause wheelspin. Make sure you have the traction control turned off. Shift around 5800 like you said. The turbo loses efficiency after 5500. Start shifting around then and keep your foot in it a bit to keep the turbo spooled.