It won't run without the foam, period. There should be a vast difference between foam and no foam. the foam block should be about 1.75" wide, so it blocks that much of the intake.
I have had issue where folks think everything is right, then they realize the snorkel is missing from the airbox. There's so much surface area the foam has almost no effect. You must have the snorkle. The airbox also must be free of cracks, holes, etc and the hole in the top / center front where the pair valve hose goes must be blocked or the pair valve hose inserted. If using the pair valve, be sure it's not leaking internally.
My jetting, when the airbox is right, has very good throttle response with no hesitation. Hesitation tells you you're getting to much air from somewhere. HTH, Steve