TurboTerror

Sorry to revive this again and being that its been almost 7 years you may be fully aware of this now so this is more for posterity of people researching the topic than a correction to your post. The point of this type of spacer is not to increase intake / plenum volume but to increase the runner length. Runner length directly effects torque production. As a general rule the longer the runner the more low end to mid range torque will be produced but you sacrifice high rpm / peak power output. Shorter runners do the opposite in that they tend to increase high rpm / peak power but sacrifice low / mid range torque. Of course all this is also dependent on the application, but in a lot of applications small changes in runner length can make a huge differences in where and how power is produced. Anyone looking for more in depth info on this subject can find in on Engine Masters on MotorTrend On Demand or watching Richard Holdner on YouTube.