My '99 SVT just exhibited this exact problem this morning. I have about a 1/4 tank of gas so I will top her off at lunch with good stuff (Sunoco Ultra 94) and put some STP Water treatment in to be safe. I run Techron thru at every oil change so I'm not too suspicious of injector clogging. If that doesn't solve it I will try (in this order)

1) Fuel filter (I did this 15000Km ago so not too likely but I might as well eliminate it).
2) Clean K&N (or put clean stock filter back in to try)
3) Clean MAF
4) Plugs and Wires (I have 65000Km on originals)

If this doesn't work I guess I am at the dealer. I suspect its the fuel pump if I had to make a bet but I thought I would do the cheap and normal maintainance items first.

Any comments / suggestions would be appreciated!

// Chris Root
// '99 SVT