89 probe gt turbo TURBO LEAKAGE

i have a 89 ford probe gt turbo and i can here a air leak coming behind the dash board on the drivers side when the turbo is engaged why is it doin this ive checked all the lines everything looks good . the turbo was recently rebuild and it would be sweet if i could get full boost iam only getting 6 pounds eny help to what this is would be sweet.