We've had Cool Guys AC & Heating out (Lynne) several times for different things for our house and our in-laws house and if it's structural like adding a new HVAC vent or something straightforward on troubleshooting then these folks are good, well-priced and ethical.
But for complex or weird HVAC behavior, we ended up wasting money on a service call (and who can waste money these days?) to Cool Guys (Lynne) and decided to call another company we also found through yelp who was able to diagnose the weird issues and actually fix the problem in one visit rather than the multiple visits we would have had with Cool Guys.