Here is another factor to throw into the mix:   Calibration of the MP
gauge.  A gauge that is off even a little can make one system look a lot
better or worse than another.
I own two different MP gauges that did not agree with each other.  Using
annually calibrated test equipment, I determined that one was right on
and the other was way off.(both were new, so much for assuming
new=calibrated) 
A gauge of unknown calibration can still do a good job showing the
before and after comparison of an aircraft mod.  I just wouldn't put too
much faith in the absolute numbers.  A small discrepancy in the MP
reading could easily be misinterpreted as a large loss of dynamic
pressure recovery.
So many details.....

Chris,

 

I agree completely.  Let's race sometime - but you must give me a head start.

 

Hey, how about in flight calibration of the airspeed indicator?  I forgot to mention that in my original missive, too.

 

My friend Arnie (rammed IO 360, Race #96) was going up to do some tests but was not happy when I asked him to record Baro setting, MAP before engine start, OAT, Airspeed, Altitude, MAP, RPM, fuel flow, yada, yada, yada........... 

 

I have considered getting a calibrated pressure sensor and then plumb it into switchable pressure sources: static, manifold, upper and lower cowl, blood, etc.  Just to see if I am achieving the theoretical values.

 

Now, for a small blower, capable of just a few inches at 8000 feet.....Mmmmmm, Mmmmmm, Mmmmmm!

 

To make a few good holes!