After about 10-15 minutes, the engine starts to struggle, as if it's starting to run out of fuel. Thanks to a suggestion in a post I read on this forum last year, I now reach down and open the fuel cap, allowing air into the fuel tank, and the engine revs back up to normal. I have to do this 3-4 times per mowing. My question is, should I drill a tiny hole in the gas cap to cure this problem? Or is there another solution?