My engine is running too hot on ethanol. What should I do?

[Ariel]

Last spring I bought a conversion kit for my Corolla from David Blume, had a mechanic install it and have been using E85 since then.   Recently my husband changed the spark plugs.  They were white, indicating that the engine had been running too hot.  Now he wants me to switch back to gasoline so I won't ruin the engine.  He also doesn't like the fact that the engine doesn't start up right away.  Can someone tell me how to remedy these problems?