Hey mate, as sumo said already dont go increasing boost just yet. If you have to leave it stock for a few more weeks til you can afford a decent 3 inch exhaust and filter then so be it. Id say the auto is just shifting at 6,500 because the ecu is determining this to be the most appropriate engine speed to shift and remain in the power curve. My auto is stock and will shift at 7,200- 7,300 if the gas is held open but the shifts are noticeably smoother at about 6,500 6,700 so I wouldnt be worrying about that too much. As far as the tyres are concerned mine is wearing 225's on the front and 235's on the rear, I dont think you'll be getting too much traction with 205's on the rear even with the car in stock condition. Hope this helps and hope you enjoy the new ride.
Take it easy,
Ryan