A top mount intercooler is basically a heat sink. Not to mention after you shut the car off, that intercooler is now being heatsoaked. So lets say you do a couple of sprints, then come to a complete stop. Once you go again, it will take a good minute or so for all that heat to be pushed away from oncoming air when you're moving. So dont expect to be super fast all the time in the summer time.
FMIC's are usually for people who track the car. BEcause it constantly needs that rush of cold air coming in.
I noticed a drop in about 15 degrees (heatsoak) in the summer going from a stock mount to a front mount intercooler.