There is a simple fix for the problem with the tubing cracking or melting at the muffler pressure tap. Use silicone!!!!
The vent/pressure line does not have fuel fuel in it except for the moment you pump a little fuel into the muffler.
This my 3rd season with an early nonpumped Evo 15cc. The first season I had no end of problems with the vent line. Last year I decided to try some silicone Dubro fuel line. I figured maybe I could get through the season, well it was in such good condition I saw no reason to replace it. Still going strong in season 2
Pete