Very professional and effective at resolving the only real issue on my 6.6 LMM Duramax, the restrictive exhaust system. Now with new software and a very clean exhaust tune, I have dramatically improved horsepower and mileage. Really wish I had gone to Dunbar's Automotive in Vernon sooner as I love my bulletproof GMC Sierra 2500 HD, owned 12 years no problems. With countless of these diesel exhaust conversions under their belt Dunbar's can't be beat. Thanks Leroy and Ken! Craig