I guess that no one reads my posts. I have mentioned numerous time that you can do a superb job of measuring your PICS actual speed by
using a routine such as:

DEFINE OSC X

LEDON

For X = 1 to 60
PAUSE 60000
Next X

LED OFF

Of course, you don't have to time for a full hour, but the accuracy gets better the longer you wait.
If have

If you use DEFINE OSC 20 and the LED stays on for 31 minutes, you are actually running at

(60/31) * 20MHz = 38.7096Mhz.

Just make sure you don't have interrupts running when you do the timing.