While upgrading the intercooler would be ideal, have you made sure you're venting as much heat out of the engine bay as possible? Is your turbo manifold, downpipe, dump tube, flex pipe and turbo housing wrapped and blanketed? That's a very cheap job, and WILL reduce engine bay temps, reducing charge pipe temps, therefore reducing iat's. Also if you don't mind the look, hood spacers and removal of the rubber weatherstripping will vent the engine bay as well. Another thing you can do is make sure 100% of the air that passes through the lower grill is passing THROUGH the intercooler, not around it. You can make plates on either side of the ic where the couplers are, preventing the air from going past them and doing nothing productive.
If you are really good at fabbing (or willing to experiment) you can cut openings in your hood, weld a mesh grill in the opening, and voila- you have hood vents. People may call "rice" on you, until you smoke them :-)
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