try removing the ic and putting the stock plastic section on. do you have a boost gauge? monitor your vacuum, see if you have running around 17 m/hg. (I think its 17, might be 11) Take a can of starter fluid or carb cleaner, and spray it on a little section of the motor while its running, if the car idles faster then you found the leak.
I bet its around the boot B section or near all the PCV junk. I had a boost leak and my car was jumping up to 0 psi at idle, and then back down to vacuum.
It also could be the way he hooked up the IC. you have to do a custom pipe set up to run the IC so he could have messed up and is leaking from that. Just put the stock pipe back one and see if you are leaking boost by monitoring your boost gauge. And if you dont have one an autometer gauge will do fine. Get something that does like 20/20 or 20/30.