For the money you can get the dutt neck for $70 and then someone to get it on for you for around $125. You will see 2 psi with that.
But if you are looking for an ic that will lower the charge to run more boost safely and get more power, then the CAS V4 or V4R NO DOUBT. There is nothing out there that can compete with its core on the market,
WHY?
Only Dequick has the newest intercooler core technology out there, extruded tube. More effeciency, more cfm at any pressure drop you compare another one to it at. At $700 and $860, you get a front mount type performance with a stock look and a great spool up due to way better pressure loss and stock route boost travel.
SVTR1, you say you are running 21 psi on the street with 93 oct?
Whats your timing? Do you have a scan tool, because it sounds like the car would have tons of kr.