How does an increase in GPS relate to power output?

[lkurek at smtpgate.anl.gov]

     Guys:
     
     Quick question for you all....
     
     Before we make it back to a dyno, is there any way to calculate an 
     increase in power from an increase in MAF readings (GPS)? Here is why 
     I ask. A buddy of mine (Brian) just did a head/cam swap and showed a 
     pretty decent increase in airflow from his previous runs. He went from 
     252 GPS to 294 GPS (if I remember this correctly) from Diacom readings 
     (could be off since he has a 96...which Diacom has a bit of trouble 
     working with). When we made the earlier reading, he was at the dyno 
     where he made 255 RWHP. Now, if I do a simple percent of increase in 
     airflow and multiply by his old HP...I get 298 RWHP. Does this work, 
     or are there other factors I need to take into account? The air 
     pressure now was higher, but the air temperature was lower than when 
     he made his dyno run.
     
     Now...the monkey wrench. On the SAME day he was at the dyno, I was as 
     well. I made 278 RWHP with only 264 GPS airflow readings. So, if I do 
     an interpolation using these numbers, I end up with nearly 400 RWHP he 
     will be making. Now, the 298hp above seems a bit light, but the 400 
     seems high (would be nice if it is correct though). So, first of all, 
     does anyone have a formula that predicts power output based on airflow 
     in GPS? Second, I assume it isn't a linear relationship based on the 
     above....but should it be?
     
     Any feedback would be appreciated!
     
     Larry Kurek
     
     BTW..please copy my Lkurek at anl.gov address so I can get your response 
     ASAP.