0 TO 2024 wasn't giving you enough range.
Code:
    ' At 20MHz, to figure a PWM frequency of 19.455kHz
    '
    ' TPWM = time period of PWM frequency
    ' PTPER = 12-bit period register PTPERL and PTPERH
    ' PTMRPS = PWM time base prescaler
    ' 
    '           (PTPER+1)*PTMRPS         257
    ' TPWM = ----------------  =  ------------ = 0.0000514 
    '                  Fosc/4                5000000
    '
    ' Frequency = 1/TPWM = 1/0.0000514 = 19.455kHz
    '
    ' PWM resolution (bits resolution for duty cycle)
    '
    '                   log(PTPER+1)*4)          3.01
    ' Resolution = ------------------ = ----------- = 10 bits
    '                      .301                       .301
You have PTPER at 2024. PTMRPS at 16. Plug these into the above, and you get 0.00648.
1/0.00648 = 154.32 so you have a PWM frequency arouund 154hZ.

Your resolution is about 13-bits. %0001111111111111 = 8191.

So 8000 instead of 2024 is just giving you full range duty cycle.