hmm, does A/C make any difference?
and also, did you try to run 4ga cable from alternator to battery, and from battery negative to chassis, just to be absolutely sure battery is actually getting all the juice from alternator? cause if ECU detects that it needs more power than it's actually getting, it will get the revs up to compensate.
Blue SVT 2002
Our Lady of blessed acceleration
...that should be written as 'The First Law of Internet Forums'