diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index fb6dee37b..9ce55d0bb 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -274,7 +274,6 @@ namespace Slic3r {
         // Otherwise, leave control to the user completely.
         std::string toolchange_gcode_str;
         const std::string& toolchange_gcode = gcodegen.config().toolchange_gcode.value;
-//        m_max_layer_z = std::max(m_max_layer_z, tcr.print_z);
         if (! toolchange_gcode.empty()) {
             DynamicConfig config;
             int previous_extruder_id = gcodegen.writer().extruder() ? (int)gcodegen.writer().extruder()->id() : -1;
@@ -283,7 +282,7 @@ namespace Slic3r {
             config.set_key_value("layer_num", new ConfigOptionInt(gcodegen.m_layer_index));
             config.set_key_value("layer_z", new ConfigOptionFloat(tcr.print_z));
             config.set_key_value("toolchange_z", new ConfigOptionFloat(z));
-//            config.set_key_value("max_layer_z", new ConfigOptionFloat(m_max_layer_z));
+            config.set_key_value("max_layer_z", new ConfigOptionFloat(gcodegen.m_max_layer_z));
             toolchange_gcode_str = gcodegen.placeholder_parser_process("toolchange_gcode", toolchange_gcode, new_extruder_id, &config);
             check_add_eol(toolchange_gcode_str);
         }
@@ -305,6 +304,9 @@ namespace Slic3r {
         if (!start_filament_gcode.empty()) {
             // Process the start_filament_gcode for the active filament only.
             DynamicConfig config;
+            config.set_key_value("layer_num", new ConfigOptionInt(gcodegen.m_layer_index));
+            config.set_key_value("layer_z",   new ConfigOptionFloat(gcodegen.writer().get_position()(2) - gcodegen.m_config.z_offset.value));
+            config.set_key_value("max_layer_z", new ConfigOptionFloat(gcodegen.m_max_layer_z));
             config.set_key_value("filament_extruder_id", new ConfigOptionInt(new_extruder_id));
             start_filament_gcode_str = gcodegen.placeholder_parser_process("start_filament_gcode", start_filament_gcode, new_extruder_id, &config);
             check_add_eol(start_filament_gcode_str);
@@ -1274,15 +1276,6 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
     // Write the custom start G-code
     file.writeln(start_gcode);
 
-    // Process filament-specific gcode.
-   /* if (has_wipe_tower) {
-        // Wipe tower will control the extruder switching, it will call the start_filament_gcode.
-    } else {
-            DynamicConfig config;
-            config.set_key_value("filament_extruder_id", new ConfigOptionInt(int(initial_extruder_id)));
-            file.writeln(this->placeholder_parser_process("start_filament_gcode", print.config().start_filament_gcode.values[initial_extruder_id], initial_extruder_id, &config));
-    }
-*/
     this->_print_first_layer_extruder_temperatures(file, print, start_gcode, initial_extruder_id, true);
     print.throw_if_canceled();
 
@@ -1899,6 +1892,8 @@ namespace ProcessLayer
                     // && !MMU1
                     ) {
                     //! FIXME_in_fw show message during print pause
+                    // FIXME: Why is pause_print_gcode here? Why is it supplied "color_change_extruder"? Why is that not 
+                    //        passed to color_change_gcode below?
                     DynamicConfig cfg;
                     cfg.set_key_value("color_change_extruder", new ConfigOptionInt(m600_extruder_before_layer));
                     gcode += gcodegen.placeholder_parser_process("pause_print_gcode", config.pause_print_gcode, current_extruder_id, &cfg);
@@ -2109,10 +2104,10 @@ GCode::LayerResult GCode::process_layer(
         DynamicConfig config;
         config.set_key_value("layer_num", new ConfigOptionInt(m_layer_index));
         config.set_key_value("layer_z",   new ConfigOptionFloat(print_z));
+        config.set_key_value("max_layer_z", new ConfigOptionFloat(m_max_layer_z));
         gcode += this->placeholder_parser_process("layer_gcode",
             print.config().layer_gcode.value, m_writer.extruder()->id(), &config)
             + "\n";
-        config.set_key_value("max_layer_z", new ConfigOptionFloat(m_max_layer_z));
     }
 
     if (! first_layer && ! m_second_layer_things_done) {
@@ -3146,7 +3141,9 @@ std::string GCode::set_extruder(unsigned int extruder_id, double print_z)
         const std::string &start_filament_gcode = m_config.start_filament_gcode.get_at(extruder_id);
         if (! start_filament_gcode.empty()) {
             // Process the start_filament_gcode for the filament.
-            gcode += this->placeholder_parser_process("start_filament_gcode", start_filament_gcode, extruder_id);
+            DynamicConfig config;
+            config.set_key_value("filament_extruder_id", new ConfigOptionInt(int(extruder_id)));
+            gcode += this->placeholder_parser_process("start_filament_gcode", start_filament_gcode, extruder_id, &config);
             check_add_eol(gcode);
         }
         gcode += m_writer.toolchange(extruder_id);
@@ -3215,7 +3212,9 @@ std::string GCode::set_extruder(unsigned int extruder_id, double print_z)
     const std::string &start_filament_gcode = m_config.start_filament_gcode.get_at(extruder_id);
     if (! start_filament_gcode.empty()) {
         // Process the start_filament_gcode for the new filament.
-        gcode += this->placeholder_parser_process("start_filament_gcode", start_filament_gcode, extruder_id);
+        DynamicConfig config;
+        config.set_key_value("filament_extruder_id", new ConfigOptionInt(int(extruder_id)));
+        gcode += this->placeholder_parser_process("start_filament_gcode", start_filament_gcode, extruder_id, &config);
         check_add_eol(gcode);
     }
     // Set the new extruder to the operating temperature.