If i were doing the BL i would go for a later model STI lip, like an 08,09,10 - because it has a much bigger center section which would fill that gap better.
The 06-08 works perfect on the MPS with some trimming - as demonstrated on my car - and now on premHK's car....
2008 2009 2010 SUBARU IMPREZA WRX STI FRONT BUMPER LIP REAL CARBON FIBER | eBay