Usually hesitation is caused by lean fuel condition. Most electronic problems will show up in a computer diagnostic scan, but low fuel pressure won't really throw a diaagnostic code, so that's a potential problem. The fuel line will have a test port. Find a fuel pressure gauge and see what kind of pressure you have. You'll need to look in a reference book or ask the dealer what should be the right fuel pressure. If it's low, check your regulator first. If the regulator is ok, check the fuel pump next.