There is only one Turbo Buick specific shop in the Denver area that I am aware of. Located on Broadway just north of Hampden.
Engines to Go
2860 South Elati
Englewood, CO 80110
(303) 781-9129
Owed by Mike and John Gayle. Mike, John and Pete have owned and raced Intercooled Turbo Buicks since there were Intercooled Turbo Buicks.
They have done all of the work on my car.
Hope this helps,