Force Fit XL  Also note that to maximise your results you need to work out hard and do exercises that increase the testosterone levels itself, like squats. Anything that is hard and is done with including the whole body to the process.If your protein and carbohydrate intake is as it should, you get enough vitamins, you have gone through enough creatine then tribulus terrestris extract would be a good next step...and more or less a final step. There is really no other aces up your sleeve is you are a natural bodybuilder. 

http://www.strongtesterone.com/force-fit-xl/