My 3.55 upgrade has been all it was advertised and more. I'd have to put it as #3 on the "to do" list after filters and smooth tubes. The 3.55 makes 5th and 6th usable on parkways or the freeway. Also, I've noticed the difference in street launches as far as being able to get of the line with minimal bog - just have to feather the throttle a little more to avoid excessive spin. In fact, about a week after the install I ran a similar Viper and smoked him almost solely on the ground I gained in the first two gears. I have yet to get a before/after ET, but I've heard a difference of .1 can be expected - that is probably so small that it can be explained aways by atmospheric/track conditions, but the seat of the pants feel is a definite improvement in my opinion.