This is the major problem with stims, and stim based pre-workout supplements - they will stop working after some time because your adrenal receptors will get downregulated. Therefore, there is not really much you can do to make these stims work again. Yes, you might OD on some of these stims, and yes, they will give you some effect. However, after some time these overdosed dosages will stop rendering results either, and the higher the dosage, the higher the risks you run of getting a heart attack. Besides, stims will increase cortisol levels, which is a stress hormone that will make you get additional fat, and will affect many aspects of your health. Therefore, I strongly recommend you to stop taking all of these stims, and start using a non-stim based supplement. Just make sure to be gradual when going off the stims, and keep in mind that you might feel like shit while going off, because these stims are addicting - literaly. Then, once you are off the stims, try using non-stim based supplements, such as DSpark. It has no stims in it, but yet it gives me amazing energy and pumps in the gym. This product is a great example of how good a supplement may be even without stims among its ingredients.