I've seen old timers clamp some clothespins on the fuel line or wrap some aluminum foil around it in one spot aboout 3-4" long. It is like a heat sink to pull heat away from the line.

I Was Surprised to see this post pop back up butt, I replaced the plugs cap & rotor, they all showed ware. the wires had 40k on them and looked good, this seemed to fix it. till the 1st part of oct. when I put my wifes 99 kia sportage 4x4 on a trailer behind the van and put a tank of ethanol in it's all the station carried it was a 90+ F degree day, it seemed to vapor lock again & again. next day I pulled it to Lincoln ne 175mi east with no vapor locking, butt it was 70 degrees out and I run no more ethanol after that 1st tank.