I've tried concentrated Mother's car wash and it works for the most part but I still have a few stubborn bug stains on the front bumper that I cannot remove. Any suggestions??

 

Try the clay bar thing.... (use a clay bar [like "Granite Bar"] with Meguiars Quick Detailer as the lubricant) and it should take it off.... Make sure you re-wax that area again as the bar will take the wax off too.