Those are the two graphs I was referring to. The plateau past 7,000 is what I am focusing on. Yes, you do not make additional power, but you are maintaining a flat power curve - which is what these manifolds primarily do. They show a small bump in power before 7,000 but carry the power up through the curve. By not taking advantage of this, you loose time on track because of the previously mentioned mechanical advantage of remaining in a lower gear longer as well as possibly needing to add an extra shift between corners. If you don't want to rev the motor past 7,000 that is your choice, but you are leaving time on the table. This graph really underscores why you might consider extending your shift point to 7,500. The ported 2018 with CIA starts making more power than the stock manifold at 5,600. If you shift a 7,500 with a 3.73 rear and 27.1" tall factory tire you will always be in a part of the curve that is making more power than the GT manifold. This is assuming you primarily use gears 3, 4, and 5 on track.