Properly configuring an EHA. Who knows?

[ps2cho]

I have established through experienced Correct FUEL PRESSURE =/= a properly functioning EHA.

I'll try to keep it short so its not confusing:
BEFORE:
300TE - Poor mpg (13-14 average)....but car accelerates great
260E -- Great mpg (20-22 average), but zero acceleration

Now I SWAPPED EHA them between both cars. NO other changes at all.
300TE -- Now I get 19mpg(wow!!) and car still accelerates great, but a tad tad slower @ bottom end
260E -- Still get 20-22mpg average and complete change in acceleration. Whole different car it feels like.
^ 3 tanks full on both. I wanted to make sure it wasn't just a lucky run.

So now I am trying to figure out the CORRECT way to make sure an EHA is functioning properly. I tested fuel pressure on both cars and it was dead on spec @ 5.6bar in lower chamber and 5.1/5.2 in upper, so how can I test it and make sure the setting is correct?

Thanks