The tall rolling diameter of your wheel/tyre package has knocked the crap out of your gearing and its causing it to lug everywhere. eg wider opening on the throttle just to maintain speed and on the hills , Not being nasty, so don't take offence, I reckon its nearly flat to the floor or you're throwing it back through the gears revving it like mad just to maintain some momentum, on the slightest incline, Even though they are a 2.4 they only pump out 75KW and 185NM of torque. One way around it, is swap diff ratios out, but now we are talking $$$$$ for minimal gain. Think back did it start to use fuel when the wheel tyre combo went on