Rough running `98 Windstar 3.0 V6

From cold, I start the van up, and if I just slightly crack the throttle it will start running rough. I think it goes away under heavier throttle…might just be that the rpms are up I can’t feel it anymore, I don’t know. It will idle just fine, and after it warms up it also seems fine. Any ideas where to look?
Also I sometimes hear a very small, high pitched, vacuum leak from under the hood. What are the most common items that go bad, that I should look at first? Thanks in advance, Rondog.

@Rondog

I would say the vacuum leak is actually the source of your problems

A vacuum leak can certainly contribute to a rough idle

Advice:

Pop the hood

Let the engine idle

If you hear the vacuum leak, try to zero in on it with your ears

Stay away from moving parts!

Vacuum tees and elbows commonly rot out over the years

Food for thought . . .

@Rondog

Nice dogs!

What kind is the one to your left, the one next to the taillamp?

Thanks for the help. I’ll dig around in there and check the vac lines.

That is a Sheltie/American Eskimo mix. He is very high energy, but very smart. I use the van, and old USPS mail van, to haul retired racing Greyhounds to their forever homes. I volunteer at FastFriends.org