two good places to start...

intake manifold gaskets.. do a search.. stock torque specs specify that the bolts be tightened down really tight, this has led to squishing the gaskets too much and causing leaks.. there has been a technical service bulletin about it and the new torque specs seem to help, or maybe its an improved gasket material.. dont remember, but as youll find in a search, with your engine running spray carb cleaner around the seals and listen for the engine rpms to change (i forget if they shoot up or stall... search will tell you) if your engine reacts to the spray, youll know you have a leak in your gaskets

easier/cheaper fixes i would start with... fuel filter.. easy do it yourself job.. its located just inside the passenger side frame rail about in line with the VehiCROSS logo on the pillar

fuel pressure regulator.. VXs commonly have trouble with them, not really sure why....

clean your EGR valve..

maybe even try running some seafoam through your engine and gas.. see if that helps good luck!