I previously had an s3003 servo and when I bought the s9550 servo I did notice a big difference in response time. I now have a Sanwa M8 and haven't tested it thoroughly at the track but had a play around with it up and down the street and it seems the same mind you the M8 has so many different set up options and it has a setting for steering response and throttle response which I haven't played around with yet. The Futaba 2PL I had previously didn't have those functions and was very basic.
I am not familiar with your controller or receiver. They aren't on the Futaba website, are they old or discontinued? The RX i was using with my 2pl was a R152JE
http://www.futaba-rc.com/radioaccys/futl26.html