hey guys my problem is that when my car warms up(it doesn't do it when its cold) my car will be hesitant and start to buck. It does this in all gears at any rpm range and will also do it at steady speeds. I have fixed the spark plugs,ignition wires,throttle position sensor,and a vacuum leak in my intake hose. I now suspect it is a fuel pump or a fuel pressure regulator. Anyone that has any information on this, I could use your help. Thanks

Chris