Don't take any detox kits.. ive heard that those things may cover it up but they can still find that you did SOMETHING to mess up the test.. Just drink alot of water.. bout 2-3 liters a day and piss as much as you can.. I'm clean now and Ive been a heavy smoker for about 4 months.. tho you only have 4-5 days.. I'd still say I doubt youve smoked as much as me.. and if you drink 2-3 liters a day and piss a whole bunch theres a big chance you'll come clean just like me.. hope this helps