Change the FUEL FILTER "first" before doing anything else!!! Fuel filters by nature are very fickle. Once your fuel filter is clogged, it's clogged for good and the only cure is to replace it. All of the symtoms you describe relate to a clogged fuel filter.

If the problem still persists after a new fuel filter is installed, then look at the fuel regulator as a possible culprit. However, I strongly believe your problems will go away by simply changing the Fuel Filter. In addition; use high octane Premium Gas, if you don't already. You'll be amazed how well the VX runs with a brand new Fuel Filter and high octane Premium Gas!!!