Best for someone more knowledgable than I to reply but my problem is not the berks but the combination of the up rev I had done prior to the berks and the berks. The up rev made the car run lean, the berks do that too making the car run very lean, hence why I need the up rev modified. Just berks should be fine but an up rev is a good idea to get the most from them.
Regarding you worry about the mid range rasp of the berks, I can understand that, I was worried at first but noemi know it's a characteristic of the berks I'm not worried, I kinda like the sound. It only occurs when the car is under load between 4-4.5k revs. I would never go back to the old cats, car was way too quiet.
Thanks for the info