Heavy Up should have been thrown away!
Absolutely!
Most likely this song is a "gift" to the person by whom it was originally inspired, just like Monteleone. Mark keeps a secret about who it is, which is kinda surprising.
I remember MK said that the idea for Heavy Up came from a conversation with Bob Dylan, he said to MK about an argument with Bob's manager and Bob used that expression with the manager.
"his response to being told to “lighten up” was “I’ll lighten up for you if you’ll heavy up for me.”
That's what MK said during the DTRW promo interviews, which can be found in the thread dedicated to that record in this forum.