If it's a turbo plug, pull the plug and put it back in again making sure it's snug. If it still leaks try a new plug.
If it's a standard plug, do the same, but make sure to use a new copper washer...or put a new plug in with a new copper washer.
It won't run right with a leak around the plug. It's not reaching full compression.
I'll race electric when batteries smell like nitro.