LS6 rpm drops

[Bigmac211]

I have an 01 z06 I bought recently that has a BTR stage 3 cam, PRC stage 2.5 heads, headers and exhaust, LS2 throttle body and FAST 92mm intake. When I bought it it had a bad surge when blipping the throttle and when you?d come out of gear to stop. It would surge from 200 rpm?s to 1300 searching for 950rpms. I got tunes from Mail order tuning and Casey told me I have something mechanical such as a vacuum leak going on after 5 unsuccessful tunes. I smoked my car and did the ether trick and have found no vacuum leak. Car drives and idles fine but if you blip the throttle it?ll drop 400 rpm?s then find 950 to idle and does the same when coming to a stop. Any ideas on where to go from here I?m pretty new to the tuning game.