I couldn't agree with this statement more. Make sure you ask around and dont take any one persons opinion for gospel. Most importantly investigate the workshops personally. Just because a workshop has been able to make some "big" power on "some" cars doesnt mean jack. You need to find a workshop you can trust with your car, that will work on your car properly, not cut corners and shoot straight with you about whats wrong. There is no point taking your car somewhere that you cant have a conversation with the mechanic about whats happening and what needs to be done. IMO this is one of the most essential things, if a workshop owner/mechanic/whoever is working on my car, isnt willing to talk to me about whats happening with my car then I dont give a sh*t how good he thinks he is, he's wasting his time being in business....at the end of the day they are just selling a service like anyone else, dont be treated like a tool because they think they are top sh*t.....because there is plenty of other places you can take your car that are usually just as good, if not better, that will be more than willing to take on your business.
And yes I am speaking from experience.