I'm looking at buying 9PSI - 11PSI BOOST PULLEY UPGRADE KIT WITH BELT L67 SUPERCHARGED 3.8L V6 for my VT. What else do you recommend to get the most out of it?

Other items consider are listed in our L67 3.8L Supercharged V6 Budget Package, as shown in the link below:
http://mace.kayako.com/Knowledgebase/Article/View/96/143/1-l67-38l-supercharged-v6-budget-package

For further ideas as to what is possible for your L67, please refer L67 Performance Packages page, as shown in the link below. 
http://mace.kayako.com/Knowledgebase/List/Index/143/l67-38l-supercharged-v6-performance--kits