I will try and combine several responses here.
Yep, I know that I could not have had 257 HP.  For one thing, the RPM would have had to be up around 8K to develop that much, and for sure I would have turned that prop at higher than 4200, BUT it still looked good on the EM-2! :>)
I have been wondering how to tell if I have a leak in my intake manifold.  Since I built it, a leak is a definite possibility.  I just haven't figured out a way to test it without building some elaborate fixture.  I assume that since the EC-2 operates off of manifold pressure, it will correct for a small leak. (add fuel to compensate for the additional air??)
The plugs that I sand blasted were the Iridium plugs.  They are pretty open and can be inspected prior to install for sand.  I agree that sand blasting the RX-7 plugs would be a mistake since the 4 grounds have the bottom of the plug almost closed off and they could not be inspected.
What is the current accepted technique for cleaning plugs?

Bill B