Does anyone know if the Kinetix Velocity manifold and the motordyne plenum spacer are compatible with each other? Or is the Mrev2 and plenum spacer a better combo?

 

Kinetix SSV and Motordyne spacer are not compatible with each other. Get the Motordyne, it's proven to work.

The Kinetix doesn't do anything unless you're FI, and in some cases has been proven to be detrimental to NA cars.

 

If I'm not mistaken, you completely remove both the stock lower and upper plenums to install the kinetix. Without a stock plenum, there's no use for a plenum spacer, so no, the two are not compatible.