Ernest,

 

I chose to keep the oil injection system.  That system has a clean air line from the atmospheric side of the throttle body to the injection ports.  With prolonged operation at or near WOT, injection oil would work its way back up that line to the throttle body inlet.  A check valve was needed to prevent this from happening.  At or near WOT it appears that although the average pressure at the oil injection port may be slightly less than atmospheric, the dynamic nature of that pressure may prevent that port location from being very effective at scavenging.  For what it is worth, that’s what happened with my installation.