I can only assist with the transistor itself which is good to 250 MHZ so at 20 MHZ is well within its frequency limits. If timimg is a concern you may wish to go with the faster 2N2222A. You might also wish to go with a 4.7K, and then consider creating a darlington configuration (collectorof transistor 1 to collector of transistor 2, emitter of transistor 1 to the base of transistor 2, base of transistor 1 to the resistor to the PIC and the emitter of transistor 2 to your LED's). My first guess is that your are not turning the transistor on hard enough. Best, Ed