First, check out the link whiplash2411 posted (kudos, by the way!). If you need help on your timing, then you need to time yourself. Set up your stopwatch or use the GMAT Timer
You seem to already know your average time to complete an RC question. From now on, try to reduce that number a little bit each RC practice session that you do. Maybe try speeding things up by 10 seconds or so the first time. Also, the additional pressure of performing under timed conditions will help mentally.
I would also try some LSAT RC
questions and time yourself on those. These are generally longer and more difficult than GMAT RC questions, so if you can handle these under timed conditions, then you will be in good shape!