Horsepower difference ?

[Hib Halverson]

>Mild port/polish on intake and exhaust ports.
>better blending of the ports just above the valve seats
>Three-angle valve seats
>"Sleeve spacer" between the head and injector housings to improve alignment
>Revised cam timing but cam profiles remained the same
>Revised calibration
>New exhaust manifolds...which actually cost 5-hp but went to production to solve a problem with the engine ingesting debris if the cat converter substrate failed at high rpm.