The stock timing is 10 so being set at 6 isn't doing you any favors. If it's intercooled and you use good gas you should try 12 and see how the car does.

I don't know what to tell you about the poor gas milage. Have you checked the plugs? It sounds like it is running rich (obiviously). Is your 02 sensor plugged in and working?

Slow boost is usally do to a boost/exhuast leak. Might check you actuator and make sure it's nice and tight.
What cam did you put in?