Each to their own, on my old P38 we changed it put the wrong stuff in "it'll be reet" and the car was certainly different far more mechanical drag and economy dropped a couple of mpg, changed it again and she was back to her old self. What i'm getting at is rather than finding a vehicle that should be capable of keeping up with modern traffic slow and struggling on the hills, check there are no faults with it first before turning up the boost and destroying the gearbox