i find the jaco foam seams to work better for me as far as traction then any other brand. as far as chunking or peeling. I find that the yellow as jack puts it chunk. but i find the case to be that the more you put latteral pressure on the car, the more they have a tendency to "chunk". running stock i find that my car does not put as much lateral load on the tires as in super stock. so I find that I "tear" the tire less and therefor chunk less. I can agree that superstock I have less control then I do in stock. but as other have said even in a clean run, i have had chunck in my tires. but more in superstock then in stock. and before the new speedos with the advanced timing, i hardly ever chunked my stock tires.
on the flip side, I am not sure I would want the foam to change much. I really do like the traction the yellow provide. when I started the "hot" setup was purple/gray. that is soo much harder to drive then yellow/double pink.
if there was a way to keep the traction level of the tire and make it less proan to chunking, that is what I would vote for. I find that the wear characteristics of the yellow tire, i am really ok with. I run a set of double pink/yellow for 2months+. I do run them a little big at the begining (44.5mm front) and run them a little small (39mm) but i have not found that I loose too much speed. I would say maybe .1 or .2 from big to small. but it is club racing.