Couple of cans of carb cleaner (o2 sensor safe). Spray a can of the cleaner into the intercooler, then take a water hose and fill up the intercooler with water. Slosh the water around in the intercooler and dump the mixture out, repeat the procedure untill the water is clear when you dump (may take a few cans). Hook up a vacuum to one end and let the vacuum dry the inside of the intercooler out.