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.

Thanks Grant! You reminded me about how important the headers are.... Years ago I followed this forums advice as well as tuners like AED and LUND who said the first thing you need to do is put in the LT headers as that was the weak point of the stock setup. These dyno sheets might look a whole lot different if the bottle neck is removed from the exhaust side of the engine.

A pair of Kooks long tubes with catted xpipes left me a 403 rwhp with everything else stock. Since then the TB, CAI and ported Boss manifold have just been building on that... Hopefully around 430 rwhp...

I really like your chart, extending 4th by 10mph is quite a lot! My fuel start cutting at 6800 right now, so even going up to a safer 7200 would already yield 6mph. That is a heck of a solid argument.

I have another car sitting here with a motor that was ruined in no time by over revving to an amount that was deemed save by many. Naturally I am pretty hesitant to go up in revs now. At least without the added safety net of upgraded springs and upgraded cooling. That said, this is something to aspire to.

Right now, the stock manifold is back on the car. I can`t use the CAI and the manifold together for the upcoming competition and the 2018 makes less power unless I have both.
But yes, It looks like these graph's would look different with some proper headers. I noticed that tvery graph looks slightly chocked from 6000 on, no matter what tune, intake or manifold.

Just for reference.... this was my last trip to the dyno some time ago with a Lund tune and Just Kooks LTH with cats.

I also agree with Grant that the first change is a move to long tube headers. They provide an across the board gain that starts in the mid-range and extends through the top end. They also provide a foundation for maximizing gains from an intake swap and / or CAI.

I meant to explain further,

I think long tubes are the first change to make. But, the intake manifolds will make more power without them - but the change is not optimized nor will an intake alone give the benefits of the header by themselves. Case in point:

steveespo said:

Baseline GT with Steeda CAI and Brenspeed tune was 379/400, Boss 302 mani and Steeda tune was 403/389, Boss 302 with Steeda Tune, BBK 85mm throttle body, and Steeda Boss CAI and ARH headers was 431/390, CJ Intake with SCJ Mono blade TB, Ford CAI and the headers 449/407. All numbers on same Dyno-Jet SAE 5 smoothing.

Click to expand...

I will have to see if I can find a graph of a header only change with a stock baseline plot on the same graph. The benefit really shows itself under the curve with the increase in mid-range and power that carries through the rest of the RPM range.

I clearly underestimated how much more exhaust flow and revs the 2018 needs and overestimated how much power gains a tune and a CAI actually makes.
For this weekend I am back on the stock 11 manifold. Competition points, time constraints and performance work out better that way. I`ll get the 2018 back in when it´s time for some headers.