Hi and welcome to the forum. No this is not normal. Your car should pull strong till it hits the limiter around 155 to 158. First thought would be the IC punp going bad. This is a fairly common problem with the SRT and is a well documented fix and not real expensive. I have replaced the IC pump on both my cars with the Johnson 30. With the pump not working the ic heats up and the computer pulls timing and cuts the power drastically. You can tell this is your problem if the power comes and goes. I am sure some of the wrench turners will come on and explaine it much better. Enjoy that SRT it is an amazing car.