Before update 1.5.68 the Clue Booster could be upgraded four times; the amount of clue boost was up to four times the normal amount. After the update this has been replaced with a 10 part progress bar. Upgrading the clue booster now only lengthen it's duration.
Upgrades (after 1.5.68)
The following reason for adding it to the list has been given: Costs for upgrades missing because they were already unlocked in my savegame. Further reasons might be found on the "discussion page". --Wile E. Coyote (talk) 10:33, 15 October 2015 (CEST)
The first four updates can be bought with coins, all other upgrades cost gems.
|9th Upgrade||50 seconds|
|10th Upgrade||200 gems|
Upgrades (before 1.5.68)
|Base||Clue Boost 2x and lasts 20 seconds.|
|1st Upgrade||1,085 coins||Clue Boost 2x and lasts 25 seconds.|
|2nd Upgrade||1,575 coins||Clue Boost 3x and lasts 30 seconds.|
|3rd Upgrade||2,450 coins||Clue Boost 3x and lasts 35 seconds.|
|4th Upgrade||3,325 coins||Clue Boost 4x and lasts 40 seconds.|
Note: 2x means "in addition to the the 1x without Clue Boost", so actually every collected clue is three times as powerful. The same goes for 3x and 4x.