I personally go to Frank who owns Revolution Motorsports which is near the speedway. He's a good guy, and very knowledgeable, but usually has a waiting list to get into his shop.
https://www.revsc.com/
There's also Gil from HP Specialties which is also near the speedway. I've never heard anything bad about him and he just worked on and tuned my buddies CTSV. I've also been thinking about going to him for a retune, because he seems to be a great tuner.
https://hpslv.com/
Garth from Leading Edge Performance (LEP) does mostly LS stuff, and seems to be a cool guy anytime I've talked to him, but over the years rumors on forums and in the streets has it that he screwed people over. However he does have some high horsepower cars coming out of his shop. You can decide for yourself.
https://www.facebook.com/LeadingEdgePerformance/