If you take the foam out, is the problem there again? I think that the fuel line routing did not cause the hickup hesitation, but a slightly lean condition did, like posters before also suggested.
The foam cause some extra air draw resistance, and that may have solved it. My plane draws air from inside the fuselage, and added foam stuffing around the tank makes me close the idle needle more. (1/2 turn!) Due to noise limits on our field, the carb opens just about halfway at full throttle, so my idle needle does all the work.