No valve spring upgrades needed and is the cheapest and best upgade for street and track use. Will work on the OEM ECU settings and aftermarket ECU if you want more customised settings. The item "Tomei PonCam Cams Camshaft for Nissan ECR33 R33 RB25 RB25DET" is in sale since Sunday, September 23, 2018.This item is in the category "eBay Motors\Parts & Accessories\Motorcycle Parts\Engines & Engine Parts\Other Engines & Engine Parts". The seller is "autocat51" and is located in West Covina, California. This item can be shipped worldwide.