to convert MAF readings into approximate BHP figures divide the g/s value by 0.8, or multiply is by 1.25, both give the same result.
120 g/s divided by 0.8 gives 150bhp for a standard A3. 160g/s or there abouts for a mapped A3
168 g/s divided by 0.8 gives 210 bhp for a standard S3. 200g/s or there abouts for a mapped S3
You usually won't see those exact figures of course, but that's the ball park you're after
Stolen from another forum...Hope this helps ;)