GM recommends 6-12", and on the upper 1/3 of the pipe, between 12 and 3 usually...and the issue with having a super short intake or putting the MAF right in front, is that supposedly the air turbulence is too great that close to the TB, and the subtle changes in TB position cause erratic changes in air flow across the MAF and can trigger running and fueling issues. IIRC, MAF failure can cause the pcm to use a different or adjusted table (don't quote me on that part, but i swear I've discussed it with someone here before)
fwiw, this is the intake setup I'm using. The MAF is about 11-12" inches away (max that my harness reached), and clocked to about 2 oclock.
