I wouldnt mix the caffeine/aspirin with the Clenbuterol, but some use T3 with Clenbuterol although this could affect your thyroid (I believe), what you can do is Clen 4 weeks then an eca - ephedrine - caffeine - aspirin stack next four weeks, or alter the 2 every 2 weeks, i did this years ago, worked really well.
G