Okay I would first start by replacing the fuel filter. As far as your fuel pump you can test its pressure once you have a new filter on. However, I am sure you will find that it is fine. I would also check to make sure your sparkplugs are all tight. I have had it happen and if you follow this link>(copy and paste)
http://www.toyota-4runner.org/showth...hreadid=15446, you will see I am not the only one. A loose plug may give you that Stumble. I had a loose plug, and that is what was going on with mine. Check your air filter, and air pasage ways be sure they are clean and clear. Good luck and keep us informed.
Cheers
P
PS if you go to page two or three someone has put up a how too for replacing the fuel filter with pictures!!