not necessarily... i`ve gotten ported factory TPI manifold equipped 350 vettes to break into the high 12`s in the 1/4. on street tires, 3.07 gears, and the factory PROM still in the ECM...SweetS10V8 said:TPI and performance are oxymorons. TPI was designed for the 305, not your 400. Will it work, yup. Will you hit a wall at 4000RPM, yup. So if your idea of performance is below 4000RPM, go for it.