just to highlight something that is important beside the intercooler itself, the pipings too. Depending on the material used, and the workmanship of the welder to bend curves, pipes routing you may gain/lose horse power. Yes indeed that the larger the i/c, there are lags present, however, do not forget the fact that if your intercooler has bigger surface exposed thus more cooling efficiency leads to better horse at higher rpm, and in my case, extremely noticeable.
I would suggest instead of getting a cheap china brand bling bling i/c, go for second hand stock evo intercoolers, i got my evo8 intercooler for RM8xx including the pipings, there are mods involved in creating the piping loops, however, nothing beats stock intercooler pipings, the curves are perfect, not pieces mashed together. Even after some heavy boosting, i can still touch the pipes and they are only midly warm, vs my friend's GSR using china brand i/c, it heats up very very fast. and really burns your finger when you touch it.
Just my 2 cents, correct me if im wrong :wavey: