Hi Tartans, as far as Volvo "specialists," there's INDEPENDENT VOLVO, SAAB, JEEP, & SUBARU although I've never had any encounter with them. Personally, I've had good experience with SilverArrow Autohaus although they're a "European" specialist.
Both these shops are in the Mira Mesa/Miramar área.
I currently have Car Diego working on an S40 T5 AWD that I bought nearby that had a BHG. They're not specialists, but they're my local go-to and they've worked on many of my other cars. They do good work and they're also very highly rated on Yelp.