the key to clen in my exp. is to work it up, as previously mentioned. Start low, 20-40, and get it up as high as 100-140 for a max length of 2-3 weeks, then take a break. If you have a lot of experience with E/C use, drink a lot of coffee (and are used to lots of CNS stim), you probably will experience less intense effects overall. It is different from a normal "stimulant", but it'll probably make you shake as you get accustomed to it. Sh!t works, though. Just don't fall into the trap of running it endlessly, as you'll defeat the purpose. ALternating 2 weeks clen with 2 weeks E/C, 2 clen, 2 E/C really seems to be a winning run. Then, if you can stand the idea ( I usually can't), take a 2-4 week break from both, let your system normalize, and the next time around the effects will be strong and effective.