I really (still, again!) have no idea what you're saying.
40 MPG isn't that difficult. I have
almost broken 50 MPG with my CRX, which the EPA thinks should get me 30 MPG on the freeway. That's in an old-fashioned inline-four engine, not the oft-lauded three-main boxer, BTW.
Small things do add up. I'm surprised that you could double your MPG just by removing the EGR system from your engine; my only thought there is that the existing system must have been really severely messed up! But I'm not surprised you noticed some effect from that, or from your fuel tank vent being plugged. Systems that are broken, or not functioning as originally designed, can definitely hurt your efficiency.
-soD