Chet, Sadly this is an all too common problem; my mother purchased a custom modular from a highly reputed manufacturer, we found problems, and I wound up taking care of most of them, as the manufacturer made many promises but kept few.
You can hire a private inspection to document the problems, which may help you in prodding the manufacturer into action, but be prepared to wait; many modular/mobile manufacturers have a looong "to do" list, and often you'll have to "take a number and get in line."
What we did personally was to contact the manufacturer, told them what little repair work which had occurred up to then was substandard, and therefor I would be performing the balance of repairs needed, and to expect my bill for services. We were reimbursed, but only after some re-negotiating.
One website on which you might find some additional help is www.hadd.com. This site is somewhat "extreme" on some issues, but does have some good advice and contacts for problems with manufactured housing.