@pandareno1999. answered a similar question earlier this week in regards to Boss Hunt.
I wish we had the hunt as well. I set aside millions in coins every few months for the minion booster packs. Hopefully they will surprise us with a battle very soon!!
Hotrod: the engine rev comes when digesting zombies. This can be done 3 ways; burrow and come up from under ground, approach from behind and approach in front, plant spike weed and then digest. The rev gives a speed boost once zombie is digested that allows you to move very quick to next target.
With all plants and zombies, ability upgrades are key to showing off their full potential. Typically the best upgrades are available between advanced 9 and elite 5. Its been a while since I played hotrod but I believe there are 2 speed upgrades and digestion upgrades.
Hotrod is the fastest character in the game with speed upgrades and that makes him fierce in Taco and Gnome bomb game modes.
