It's funny you all bring this up. I was doing some research in my A&P class and came across an index in the back of my text. It turns out asprin actually releases ketones, which are typically released during ketosis or when someone's on a ketogenic diet. Now, ketones have been shown in studies to be very damaging to the kidneys, but the bottom line is, a ketogenic diet does in fact allow for an individual to get really lean.
Bottom line, whether or not asprin really enhances the effects of caffiene and ephedrine, while one is on a ketogenic diet.....I don't know. It doesn't hurt to take a low dose asprin with your C and E, meaning something around 150-200mg. The typical 325mg is too much. There's no need for high of a dose. But if you don't have any, don't worry about. Caffiene and ephedrine are the main culprits acting in thermogenic process.