Bubble Gum
When taz is chewing the bubble gum, blow it up until it just starts to go red, then stop for a couple of seconds and press the X button to inflate it again to the largest size. This will definetly get you to those hard to reach places. Also make sure Bugs gets the gum for you, while you are at the point of elevation.
Level Select
Pause the game, hold L1+R2, and press Circle x4, Square x3. A "Load Level" option will be added to the menu. Select it to open the level select.