Auto-complete in JavaScript
There's a few things that can be reviewed:

Your indentation and spacing are incorrect, use JSFiddle's TidyUp function to clean it up.

All of the e.keyCode == matches shouldn't be matched to magic numbers, but moved to a kind of enum or something similar:
var KEYS = {
    Enter: 13,
    DownArrow: 40,
    UpArrow: 38
};
// ...
if (e.keyCode == KEYS.Enter){


suggList:
Don't sacrifice readability for a few characters: suggestedList is more than fine.

console.error:
Instead of console.error, use throw instead: console.error('No sourceList provided for customAutoComplete') into: throw 'ACError: No sourceList provided for customAutoComplete'