Who did the swap and how long has it been in the car ..
Did this just start happening when you went turbo...

1st are all your wireing connected (chech everything no lose connections even grounds)
2nd are you running on the stock Ecu for the b18b or a chipped p28 or something ...

you said you disconnected the batterie while your car was running did you put a load on it like turn the lights on a/c and radio ....

and last i would check for any vacuum leaks ... thats all i can think of ...