i have audi a4 b7 tdi 170 and got it remapped to around 200bhp, then i got straight through twin exhausts fitted after. they sound ok but sometimes they sound reel deep as if it was a petrol turbo, then after 10 mins of driving they go back to what they was and dont realy sound at all, does anyone know why this is as i would like them to sound better than they are, thanks