bumping up an old thread but I would like to add a few things from my installation on an 07 WRX for future reference.
I ran into fitment issues with the stock GRB bracket so I trimmed it to make it literally an extended piece. As stated before, you can measure and fabricate a bracket at a local hardware store.
The stock y-pipe red hose is just as much of a PITA to get on as the 04-07 STi intercooler y-pipe red hose is (as they are the same size) so getting an extended y-pipe hose makes installation easier.
I was still able to reinstall the JDM STi FHI Titanium front strut bar without any fitment issues.
SPT or similar style turbo heat shields will not fit due to the extended bracket.
The Subtle Solutions GRB Intercooler splitter will fit under the 06/07 hood scoop without the intercooler splitter if you want to cheat. However, the GRB splitter sits a bit slanted due to the lower passenger bolt and removing the intercooler splitter does not allow the air to directly flow over the last 1/3 section of the intercooler so modifying the intercooler splitter is still needed for efficiency.