I took my car to a rolling road today as I was sure it was overfuelling.
After several runs and adjustments I got the AFR's right. Then we did some nitrous passes and adjusted some more.
She has a problem of making too much power, too low in the rev range. So I guess its time to start looking at a different cam for nitrous use now. This explains the manic drive up to the 1/8th mile marker, and then a fairly fast drop in power for the last 1/8th mile on the track.
But the new tune has added another 60hp and another 200ft/lbs which I'm happy with for now. Today she did 378bhp (297hp at the wheels) and 602 ft/lbs of torque.
(http://i205.photobucket.com/albums/bb270/mgbv8_photo/V8dynoplotjuly2009001.jpg)