All other loot is is perfect 2x, but you go to a box and find 15 pipes sometimes.  Can you take a look at what is blowing the pipe spawns up?

Have you added extra items ?

Make sure you don't have two loot modifiers modifying the same item. Also make sure to check your extra items as mentioned above. 

Also don't use global multipliers on anything if you are doing specific loot table editing.