Ordered the EP today, but won't be here in time for the dyno day at AWE 12/22. I may wait to install it when we have some decent weather for me to make the trip to install it at AWE and run a dyno before and after the cat/muffler swap. Stef at EP is very helpful and provided these responses to some of the questions I had asked him...

1) Our 100 cell race cats will not cause a Check Engine Light problem .
We had the original 300 cell GT3 cats chemically analysed . According to this chemical analysis our cats are specially coated for street use . The chemical coating is superior to the coating of regular race cats .
The US GT3 engine is identical to the European GT3 counterpart in terms of Lambda / O2 sensor setup .
You do not need an ECU reprogramming with the new exhaust .
However , an ECU reprogramming will indeed maximize the performance of the exhaust system .

2) The dyno graphs are from 1) stock engine , 2) stock engine with the new
exhaust , stock (not reprogrammed) ECU and stock aircleaner .

Dyno stock pipe: 385.1 PS (Hp)
383 NM Torque

Dyno europipe: 397.7 PS (Hp)
394 NM Torque

In summary: +12 HP, +8 lbs/feet torque

At the wheels before(stock): 278 (PS) Hp
At the wheels after EP: 304 (PS) Hp

That's +26 at the wheels!!! Not to mention the awesome note...

Here's how it looks installed on their demo car in their spotless shop...