2003 Hyundai Santa Fe- P0303 – Acceleration Limit

I’m working on a 2003 Hyundai Santa Fe V6 with auto trans. The vehicle has a P0303 code and it has a problem with its acceleration. It seems to run fine when you start accelerating, but the acceleration is limited to 20 mph. I’m trying to figure out if the P0303 code is causing the acceleration problem or if this is a transmission problem. Also, the vehicle hesitates when going up a small grade. Could a P0303 put a limit of 20 mph on the acceleration, or would this indicate an accelerator sensor problem? Thanks!