Hi i have just bought a n reg audi a4 1.8 turbo,someone took the recirculating dumpvalve off it and replaced it with a dump valve,the car was very hesitant and on tickover kept hunting sometimes nearly stalling,The dump valve blew up so i had to put the recirculating one back on until i sourced another dump valve,when this was fitted it ran a1,but wen i fitted the new dump valve it went back to the way it was but not as bad as last time.Can anyone help me as im bit confused,when you pull away its very hesitant and pulls back but then all of a sudden has a power burst and off she goes,it sometimes back fires out of the exhaust also.The dump valve is conneted to a pipe near the radiator and has a thin pipe coming out of the top of it which goes over to the right hand side and is connected to a long silver thing(sorry this is the only way i can describe it as i dont no wat its called)is this the correct place for it?any help would be much appreciated thanks,the dump valve is a diaphram one,also noticed when accelerating there is a slight ticking noise like a blow from a manifold??