You can do quite a bit with the 1.4, as its used in motorsport quite a bit and makes a great engine if you compete in a 1.4 class, but its quite expensive to do, and a puma engine conversion is a lot more financial sense unless you are restriceted to engine capacity classes, but I've heard of 1.4s with bike carbs (off a suzuki gsxr 750 I believe), ported heads, high lift cams and tubular manifolds doing 110 @ the wheels. But costs about £2-3k.