Good Afternoon, Jmal,
Ian is correct. MGIV is a great paper, but selenium toning has a minimal impact on the appearance of an image. With side by side comparison of toned and untoned prints from the same negative, I can just barely see a difference, with the toned version seeming to have slightly richer and deeper tonality. I also use a 1:19 dilution for about the same time as you. The only significant reason to use selenium toning on MGIV is that it might, just might, add to the archival qualities of the paper, and even that seems subject to debate.