I dunno about the S2, but in my S1, when you floored it, 2 things happened - the trans automatically switched to "power" mode, and it shut the aircon off until you lifted. The ECU in the stagea's never ceased to amaze me how intelligent it could be with things like that.
As for checking the aac valve, try this
http://www.skylinesaustralia.com/forums/Di...html&hl=aac
but my understanding of it, is that if this was the problem, your fuel economy would be up teh poopoo all the time, and it would "hunt" at idle too.