that is correct, in full reserc then their is no lag as don't have the valve releasing all the pressure each time I change gear,their is about 2 1/2 metre of 3"inch pipe with a front mount so you want to keep pressure up,you really want to keep pressure up with a top mount also,thats why oem are reserc and not vent to atmosphere.vent to atmosphere are just to give you the silly woosh noise,their is no performance gains from having it,dont see rally teams venting to atmosphere,a dump valve is basically a safety valve nothing more just to keep pressure right but people I think firstly in japan started fitting vent atmosphere for shows and then everyone wanted the noise,your car is the wrx-s don't they have the big sti intercooler fitted to them,if so I wouldn't bother with a front mount unless your going 400bhp plus,your intercooler is good for 350bhp I read,my wrx topmount interccoler are tiny crap things,mine was already fitted to car when I got it but I can tell you if you do decide to go front mount,either get custom made so can have piping as short as possible and also don't buy the perrin or other other priced intercoolers as the cheaper ebay 1's do the job just as good and cost quarter the price.