ComboBox AutoLookup behavior

Here's what we're experienceing in a part of our app written with Delphi 6:

In a TComboBox that has many items in its list, a user can jump directly to a selected item if they type in the text of the desired item **really fast**   This typicak "auotLookup" behavior really does work, but you've gotta type quickly.  As you might guess, we have annoyed users who complain that if they pause at all while keying in the desired "jump to" text, to combobox loses track of thier request:

Example:  user wants to do an "autoLookup" of list member RL357 in the comboBox

if user types in RL357 extremely fast without pausing...the combo finds RL357 just fine
BUT
if a user types in RL, then pauses for a split second, then types 357...the combo forgets about the RL and jumps to the items in the list the begin with 357 instead.

I'm hoping the TComboBox has some "window of typing time" setting that I can adjust, but I can't find anything like that.  Are we stuck with the 'fast-typing' workaround or can the combox be altered to accomodate slower typing during autoLookup?

Thanks for  your thoughts!