Had exactly the same issue with my 06' Hawkeye. Went through various combinations - simple Prodrive BB, then removed the center section for a unresonated one, then the 2nd short decat pipe (after the downpipe - does not affect MOT...), then swapped to an STI Genome BB.....
Finally swapped the Genome for a Scoobyworld AfterBurner which sounds great, and not too much drone on the motorway - no idea if it would pass a TT test though...
So to recap - phewww... I now have a 2nd decat, unresonated centre section and Afterburner BB. Their new Raptor BB sounds awesome mind...
J.
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Currently very broken Hawkeye WRX 
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