Well its been 3 years since your last post on this. Motor still going?

Reread with interest all the posts made long ago - I might have overlooked it, but I didn't see any mention of the added drag the car has been the airflow is broken up by the deployed wing. With the wing down, the air flow follows the hatch a bit longer and creates a smaller "hole" in the air.

I have a 1980 RX7 with a highly modded motor. I found out that at speeds over 130 the back end would get noticeably light. Enough to make me back off. Mazda fixed this by selling a large bolt on spoiler that fit on the back. I thought it attracted too much attention. My solution was to crank up the sunroof - old kind, not retractable. You either removed or tilted it. This seemed to create turbulence which killed the air flow over the hatch which reduced the lift. Voila, simple and easy fix.