forgot to mention so far the most I have paid per litre for 98 was $1.82 and i'd be getting 30 or better mpg or whatever the conversion is. I know the backpack does slow the car down a bit in outright pick up as once its off you can notice the effect dramatically. cruising at 110kph with pack on -6 on the digital boost meter=without pack -9 to 11 so indicates a little resistance