there are many threads that show the stock STi intercooler is better than many aftermarket ones. limiting boost to 16 with a 20G seems very conservative but you still gained 100whp over a stock STi on that dyno which must be a kick in the butt dyno. it seems laggy though. do whatever you need to do but crank that boost up. you paid for a 20G so use it.
It was most interesting to see the comparison between the 3 and 4th gear pulls. good luck.