I have a Switchblade on a B model, and a 177148 on another.
Mileage is pretty much the same, slightly better with the BW.
Quick spool and higher boost at low rpms considerably better with the BW.
Full load power and egt a bit better with Switchblade, and the Switchblade is better than the stock was.
My instinct is that the 177148 would be preferable for A Model's engine, as it performs very well with less fuel. Not having ATAAC is something to consider though, as increased intake temperature may diminish the benefit of added boost.
The 177148 is less than half the price of the Switchblade and we have had no issues with it.
Not so much an adapter as it is a bushing. The crossover pipe has smaller bell going into turbo compressor housing. This adapter brings the size down to same as the tube.
Deffinatlly worth while upgrade with those smokey A model 3406 cats.