Not if all you are doing is putting on the 1.9 head. You will have tougher cold starts and the timing will be different than "normal". If you are going to be building up the engine, than the 1.9 head would be good. However, if you are planning on a hi performance build, you should deal with the head while it's off the car, ie. port and possibly source larger valves. Otherwise, the 1.6 head is what you should stick with.