258 cams for fast street 4G63 engines with stock turbo or turbocharger upgrade. Suits upgraded turbo sizing 48-54mm. Improved low to mid-range power and good throttle response. Suits restrictor plate rally 4G63 engines. Broader power band and improved throttle response when using MIVEC. For up to 8000rpm and 25psi boost Kelford Cams recommend valve spring KVS63-BK.