If you found it to be the case in the TOEFL, the SAT should be no different.
The big thing that causes people to do poorly on the SAT compared to their practice tests is the fact that taking tests is a stressful thing, so people tend to sometimes panic and stress out, causing them to forget simple things and not do very well. If you are good at taking tests and had experience with this before, the large testing rooms should not intimidate you and there is no reason to do lower on the SAT than the practice, since the questions tend to be of a very similar difficulty level.
Questions from the Question Bank, for example, are ranging in difficulty that corresponds directly to the real SAT, aside of maybe the top hardest questions. If you are doing well on those, you should be able to score well on the test. Doing official practice tests would be of additional value, of course.