Need Serious Help - Car driving me crazy

[sephir_07]

i just got a 89 turbo supra and the other day it rained cats and dogs. 5 mins into my trip the cars check engine light came on and it started cutting out. not a miss just a strait up die and restart after about 500 rpm loss. it also lulls into the 5 or 600 rpm range when stoped. then just as suddenly as the problem came on it goes away and runs great for 3 or 5 more mins.
ive taken all the intake stuff off and cleaned it with carb cleaner. no water anywhere. i do however have a exaust leak just behind the turbo elbo i can also hear a distinct blow off nois when i shift that was not there befor.
the car is compleatly stock

any ideas anyone???

also pulled all the plugs they are all like new.. not even a little carbon on them. no oil no water.... no water in my coolent or coolent in my oil either...
man this is pssing me off