i had a straight through exhaust sounded great but noticed the fuel consumtion was poor maybe it was cos of me enjoying it. BUT i did notice cos of no back presure in the system the turbo could over spool this could wear out the turbo bearings ! makes you think.so now i have a straight through scilencer on it just to save the turbo, still sounds great though. Best advice is go for a good remap, mines 200bhp and 400ft/lbs of tourqe and still bet 30 mpg if kept at leagal speeds Give gary at td5 alive a call he will tell you all you need to know