gibsy

hi im new to this site and my question is- i recently put a bailey dump valve on my 93 impreza turbo import and ive started getting a noise down the exhaust when i release accelerator after hard acceleration. somebody suggested that the flap inside the turbo is sticking and some of the boost pressure is going down the exhaust.... could this be right if so can it be sorted??? and could any1 tell me what model turbo is fitted to my car so if it cannot be fixed i can get a new 1. many thanks to whoever replies