Autocomplete do JQuery - Busca no banco em toda letra digitada!

	 <!-- INICIO ENTREGA VALOR DO PLANO -->	
	  $(function(){
      $(document).on("click", "li", function() {
		  //Pega o id (value) do select atrelado à li escolhida
		  planoEscolhido = $("#plano").val();
		  //Pega o texto do select atrelado à li escolhida
		  planoEscolhidoTexto = $("#plano option:selected").text();
		  
		  $.getJSON('planos.ajax.php?search=',{plano: planoEscolhido, ajax: 'true'}, function(resultado){
			  novoValor = formataMoeda(resultado['valorPlano'],2, ',', '.');
			  $('#valorCombinado').val(novoValor);
		  });		  
			  
    	});           
	  });         
	 <!-- FINAL ENTREGA VALOR DO PLANO -->

	(function( $ ) {
		$.widget( "custom.combobox", {
			_create: function() {
				this.wrapper = $( "<span>" )
					.addClass( "custom-combobox" )
					.insertAfter( this.element );

				this.element.hide();
				this._createAutocomplete();
				this._createShowAllButton();
			},

			_createAutocomplete: function() {
				var selected = this.element.children( ":selected" ),
					value = selected.val() ? selected.text() : "";

				this.input = $( "<input>" )
					.appendTo( this.wrapper )
					.val( value )
					.attr( "title", "" )
					.addClass( "custom-combobox-input ui-widget ui-widget-content ui-state-default ui-corner-left" )
					.autocomplete({
						delay: 0,
						minLength: 0,
						source: $.proxy( this, "_source" )
					})
					.tooltip({
						tooltipClass: "ui-state-highlight"
					});

				this._on( this.input, {
					autocompleteselect: function( event, ui ) {
						ui.item.option.selected = true;
						this._trigger( "select", event, {
							item: ui.item.option
						});
					},

					autocompletechange: "_removeIfInvalid"
				});
			},

			_createShowAllButton: function() {
				var input = this.input,
					wasOpen = false;

				$( "<a>" )
					.attr( "tabIndex", -1 )
					.attr( "title", "Mostrar todos os Registros" )
					.tooltip()
					.appendTo( this.wrapper )
					.button({
						icons: {
							primary: "ui-icon-triangle-1-s"
						},
						text: false
					})
					.removeClass( "ui-corner-all" )
					.addClass( "custom-combobox-toggle ui-corner-right" )
					.mousedown(function() {
						wasOpen = input.autocomplete( "widget" ).is( ":visible" );
					})
					.click(function() {
						input.focus();

						// Close if already visible
						if ( wasOpen ) {
							return;
						}

						// Pass empty string as value to search for, displaying all results
						input.autocomplete( "search", "" );
					});
			},

			_source: function( request, response ) {
				var matcher = new RegExp( $.ui.autocomplete.escapeRegex(request.term), "i" );
				response( this.element.children( "option" ).map(function() {
					var text = $( this ).text();
					if ( this.value && ( !request.term || matcher.test(text) ) )
						return {
							label: text,
							value: text,
							option: this
						};
				}) );
			},

			_removeIfInvalid: function( event, ui ) {

				// Selected an item, nothing to do
				if ( ui.item ) {
					return;
				}

				// Search for a match (case-insensitive)
				var value = this.input.val(),
					valueLowerCase = value.toLowerCase(),
					valid = false;
				this.element.children( "option" ).each(function() {
					if ( $( this ).text().toLowerCase() === valueLowerCase ) {
						this.selected = valid = true;
						return false;
					}
				});

				// Found a match, nothing to do
				if ( valid ) {
					return;
				}

				// Remove invalid value
				this.input
					.val( "" )
					.attr( "title", value + " didn't match any item" )
					.tooltip( "open" );
				this.element.val( "" );
				this._delay(function() {
					this.input.tooltip( "close" ).attr( "title", "" );
				}, 2500 );
				this.input.autocomplete( "instance" ).term = "";
			},

			_destroy: function() {
				this.wrapper.remove();
				this.element.show();
			}
		});
	})( jQuery );

	$(function() {
		$( "#cliente" ).combobox();
		$( "#toggle" ).click(function() {
			$( "#cliente" ).toggle();
		});

		$( "#plano" ).combobox();
		$( "#toggle" ).click(function() {
			$( "#plano" ).toggle();	
		});

	});
     
	 <!-- INICIO ENTREGA VALOR DO PLANO -->	
	  $(function(){
      $(document).on("click", "li", function() {
		  //Pega o id (value) do select atrelado à li escolhida
		  planoEscolhido = $("#plano").val();
		  //Pega o texto do select atrelado à li escolhida
		  planoEscolhidoTexto = $("#plano option:selected").text();
		  
		  $.getJSON('planos.ajax.php?search=',{plano: planoEscolhido, ajax: 'true'}, function(resultado){
			  novoValor = formataMoeda(resultado['valorPlano'],2, ',', '.');
			  $('#valorCombinado').val(novoValor);
		  });		  
			  
    	});           
	  });         
	 <!-- FINAL ENTREGA VALOR DO PLANO -->