I'm intrigued by the Motordyne spacer concept but would like to know the answer to two questions before messing around with my plenum:

1) When folks change their spark plugs with the stock plenum, do they universally find that plugs 1 and 2 are fouled or a very different color than all the others? When I changed my platinum plugs to Iriduims at 6500 K, I did not notice any color difference.
2) When running a Motordyne plenum spacer, does this difference fully correct?

Can't see how there's an important A/F mixture difference in the cylinders without reliable telltale signs on the plugs BEFORE the mod.

 

All I know is that when I tested a plenum on an airflow bench it flowed 10% less air to the front two cylinders compared to the back two. Since the O2 sensors are only seeing an average across three cylinders, the ECM can not correct for this difference and must run everything a little richer than needed to be safe. I think the plenum spacer is one of the best investments for the money. I went with the Motordyne, because it evened out the airflow as well as the angled spacer in the tests I conducted. I also like having the spacers for the 6 bolts in the center of the plenum.

 

They're for real. Check out page 56.

 

It all makes sense now! A 3.5 engine can only hold 3.5 liters of air at one time, if the plenum can provide more air than that ,all cylinders should get about the same amount of air regardless if the spacer is angled or not, this means that the motordyne and aam spacer should have about the same results. I would go with motordyne if I were doing it all over again the iso thermal upgrade they came up with is ingenious, and the spacers provide better structural integrity, you should check it out there is a group buy going on.