I have a 2003 KLR650 with 16k miles on her. I just Got back from a 1k mile weekend ride and I am having a little issue. While riding on back roads she runs fine. But I had to do about 300 miles of interstate to get home. When running at steady throttle 75-80 mph she acts like she is running out of gas. If I flip the petcock over to reserve it runs much better. Only starved of fuel once while running on reserve. Again running back roads with varying throttle I have no issues at all. Where should I start looking?