Like Bill said.. if there aren't any alarms, it appears to be a fuel delivery problem. Either the LP pumps aren't able to supply enough fuel to keep up with the VST pump, or the VST pump screen is clogged.
Since you haven't done anything in a while, I would without hesitation replace the low speed pumps. If they haven't already failed, they will soon, and its a very easy project for short money to eliminate an easy problem.
The pumps are about $35-40 a piece and I think your engine has three of them. It will take about a half hour to swap them out, and all you need is a socket set - three 8mm bolts per pump (I think).
Cleaning out the VST tank and making sure the VST filter screen is clear is a straightforward project, and won't cost you anything but time and about $30 for a new VST tank gasket. Again, all you need is a good #2 screwdriver (9 screws) and a socket set (3 8mm bolts).
The other basic maintenance I would recommend would be to inspect and clean out the Oxygen Density Sensor and draw tube, replace the T-Stats and Pressure Relief valve. Again, no special tools required, just a 8mm socket. To test the O2 density sensor you will need a multi-meter and possibly a test harness.
For completeness sake, check/adjust the Throttle Position Sensor and make sure the oil control rod is properly adjusted. To test the TPS you will need a multi-meter, but can do the rest without any special tools.
Sounds like a lot, but trust me that these are all straightforward projects that anyone with even a little mechanical ability can do, and will probably cost you less than $200 in parts and 3 hours of your time.
These are all routine maintenance items, and should be done according to the maint. schedule in order to keep your engine happy. If you don't take care of them now, they will catch up with you and cause much larger and $$$ problems down the road.
I sit on my arse all day on conference calls and powerpoint slides, and even I can do this stuff
-- Tom
