Peak HP doesn't mean squat if you're not making power overall. For such a mile build I wouldn't even consider a manifold. Seen the charts, gains are minimal and even a loss down low where you don;t have the velocity. Those manifolds are made for high revving motors pushing some volume. The TB is a waste also at that point. Stock TB should be good up to the 550 hp mark. My stock TB flows enough to produce just under 600 hp.

 

My 07 GT has had Hot Rod cams, FRPP intake, C&L Racer CAI, Kooks LT's , 4.10's, since 2010.

The car picked up an additional 18 rwhp after the intake install. I honestly do not remember the torque curve.

It made 342 rwhp with the above mods, thats on a conservative tune with 4.10's.

Maybe its the 4.10's but I have not noticed any loss of torque, low end, start up and drive ability is like stock. So far no downsides that I have noticed to the mods.