Modern Vespa

I just looked up the fuel filter on AF1Racing -- $154!!!!!
That is ridiculous for a fuel filter.

Anyone have a recommendation for a source of a reasonably priced fuel filter for my 2007 GTS250ie?

Cut the line and fit a inline filter for $10 at the local auto store.

Why do you think that you need the fuel filter? I've worked on GTS models with 98000 - 125000km with original fuel pumps/filter - without any issues. So, why do you want to get into this messy job of replacing the fuel filter?

It has a running problem that seems like it might be fuel starvation.
It starts and runs, sometimes a bit rough, but, then smooths out enough to start riding, but, then starts to stutter and run rough, then die within 1-3 minutes of starting.

Has your 250 had the fuel pump recall?

I do not know.
When I get the fuel tank and fuel pump out, I'll check for black (recalled/bad) vs. brown pump motor.

I don't know when that will be, as I am chronically short of free time.

You may also want to try: https://cheekythoma3.wixsite.com/itsme/idle

I'll add to that - you're on a hiding to nothing with poor running problems if you haven't checked the valve clearances. I doubt that's the main problem here - but without them being right you'll never get the best performance you should, so you might wind up chasing your tail.

have you checked for air leaks? If you still have the EVAP in place, this is a good place to start looking for a vacuum leak.

will do