Supra Hesitates

HELP!! Every couple of months I had to top up the rad, i knew it was time to do it every time I could hear air moving around in the heater matrix. Idle speed was up and down, and it felt like sitting in a tractor when sat at traffic lights. occationally it would blow out a white creamy puff on startup. To me it had to be the head gasket and possible valve seal failure. Other than the above problems the car flew!! It's an otober 97 auto tiptronic twin turbo. The turbo's are 18months old stage 3 hybrids from turbo Dynamics.

I had a 1.6mm HKS head gasket fitted, and all the valve seals replaced (as they were non existant) this job was done with the engine out and they replaced a number of cracked and perrished vacume pipes etc. Everything was still like new (i've nursed this baby) no wear on the cams, and the bores still have the hone marks from new! I had a fuel cut defecer fitted as these turbos have not seen the light of day past 1bar.

The problem happens when accelerating hard, lets say from a kick down, there is a point when it hesitates then continues to accelerate, all this happens before it's changed gear. The accelerator pedal even pushes my foot up as though it's a traction control problem and yet I know there is no wheel spin, that seems to happen when changing gear. I've even had the engine management light come on leaving me with very little use of the accelerator (approx the last 1/8th movement - an annoying little mod in the last of the supras fitted to the throttle body)

The only thing I have noticed is that the switch that turns on the Air con unit, a couple of times has started flashing, resulting in the air con turning off. It's easy enough to reset, just turn it off then back on again. Anyway I started to wonder if the problems were related so I turned off the aircon and floored it, I'm not sure if it's me and I'm imagining it, or that there actually is a difference for the better, but could the aircon unit be causing this hesitation problem? If not, does anyone have any suggestions or ideas?..... Thanks guys