Well, i'm still doing my research on upper and lower plenums and spacers. Took a look at Crawfords and their designed compared to our OEM plenum makes lots of since. I'm not an engineer or anything but basic logic says it's a good design for air flow.

I've also search this site on Crawfords plenum and there are mixed feeling about their product. But i didn't see this vid so i'm posting it anyway, if you haven't seen it already take a look, it explains their product.

http://www.crawfordz.com/support/crawford2.wmv

 

pretty old vid it was on their website i believe.. but im not sure if they even still make the product anymore?

 

Well, the tests done by Nissan Sport magazine certainly favors the MD spacer overall especially in the bang for buck category.