I would recommend Finish Line Performance in New Durham. It is just off Rt 11. We've had several cars in our family worked on there and never had a bad experience.
When we first moved to the region full-time, our daughter, a nurse, was still working at a Boston Hospital. We had an old beater Scion that she used for the long commute. It needed a critical service and she needed it for work the next day. Heath fixed it promptly and she got off to work just fine. What we didn't find out until later is that he needed a $35 part to complete the service. None of the parts stores in the area had it in stock, the closest place was in Rochester, and they couldn't deliver it until the next day. Knowing our daughter needed the car for work, Heath drove to Rochester, picked up the part, and finished the work, and he never mentioned this to us when we picked it up. That's service!
Many other neighbors have had similar experience there.
http://finishlineperformance.biz/