What’s the top speed of an 03 prairie 360. Mine will only run about 30/35?

My Prairie 400 will do an indicated 50 at 1100’ but only 30-35 at 9000’.

Many years ago I rode with a 360 and I am pretty sure it would do more than 35 at 1000’ altitude but dont think it ever saw 45 but I could be wrong.