What was Marshall Faulk's ACTUAL 40 yard dash time?

And I dont want to hear some over-inflated 4.2 like a couple rumored times floating around the internet. It doesnt take a rocket scientist to realize he didnt run a 4.21/4.27. You can obviously tell from his highlights that he wasnt moving quite like a Devin Hester, Deion Sanders , or Randy Moss. So with that said what was his real 40 and wikipedia isnt a reliable source.