person working on mercedes, BMW and prado are not guarantees of him working with required tools and knowledge base, best example was in Karachi. There used to be a person who dealt with the electricky stuff of cars - he also then got customers of mercedes benz, jaguar, land rover, BMW, Audi, Porsche.
Did he work honestly? - NO! - capsat knows whom Im talking about.
Nearly everyone knows his name in Karachi - but there were others who worked properly from their little businesses and yet were unknown. You need to find such people - the way to find them is to ask mechanics if they follow the repair manual or not.