My 2003 has a vent tube coming out of the tank between the fill cap and the instrument cluster. When it gets clogged with dirt it acts just as you have described. You can also buy an aftermarket fuel cap with an air vent in the cap. Or clean the vent tube.

SJ

 

Ok, I've got my 250 running like a top ... for now. There was no blockage in any of the vent tubes and even taking the gas cap completely off made no difference.

I added some Sea Foam to the existing gas and to the engine oil and ran the gas down to less than 1/4 tank. In the meantime, I liberally sprayed carb cleaner into the air intake. I then put in Premium gas with more Sea Foam mixed in and...she is running great.

Thanks for all your help.