Here's another drill for you to use to isolate problem areas. Please remember: When you're practicing, the time you spend reviewing your mistakes is arguably more important than the time you spend doing the problems in the first place. This drill will be most useful to you if you spend some real time with the answer key and technique guide afterwards. If you just mark the drill, shrug off your mistakes as "silly" ones, and move on, you're dooming yourself to repeat them. It's important to LEARN from your mistakes.
I should also restate something I've said before: These drills of mine are not exhaustive. I'm trying to write questions that cover a broad range of possible SAT questions, but in no way can these 20 questions (or these 60 questions, if you count the first two drills too) encompass every kind of question that will be thrown your way. I'm trying to help you work out a few specific kinks, but the bulk of your work should be in the Blue Book.
The answer key, as always, is linked from the end of the drill so that you can work through the drill without peeking, but you can also access it directly here.
Feel free to print, share, etc.