The only thing I've witnessed, and this isn't from personal experience, but the most common mistake I've seen people make is that they run too much boost with an inadequate fuel system. People take the 12-14psi boost limit on the stock fuel system as gospel, not taking into account that thier fuel pump is 20 years old and probably not keeping up the required base fuel pressure. Also include blocked/leaking injectors and other fuel delivery issues, it's always important to make sure that your fuel system is up to scratch before demanding more out of it...