Ram air scoops usually work if you have ONE throttle setting.... because the mixture isn't varying at the same rate as the ram pressure. Ram pressure varies immediately because it is in the prop blast (varies) and the airspeed (also varies). I've done these and ended up with lean runs big time, great on the ground because it's more or less static. In the air, completely different enchilada.....

Now, with the ram pointing REARWARD, it's a different deal altogether.

I'll be interested in reading your report, too, zippi. Hope it works for you!

(P.S. - it sounds strong, and is turning high r's PROBABLY because it is leaner than it ever has been. Did you measure the head temp after that ground run? Remove the plug and check the ceramic color? May want to check that... )