Just watched this fifth gear clip on restoring engine power. It was very informative on how even a service and replacement it leads can bring back lost engine power.  The thing I found most interesting was when they applied Redex to the fuel system and was surprised at the increase in horse power. As seen below:  When new: 190bhp Now: 177bhp A week after Redex added: 183bhp. Have any of you had experience with Redex or other fuel additives and would you recommend them?