im buying a TII engine for my s4 n/a shell. id like to go aftermarket with the ecu and was wondering what would the best ecu be for that? ive herd good things from rtec, and a few other.

 

I'd say a few of the most common would be RTek, A'PEXi Power FC, and Haltech... There are PLENTY of "standalones" out there for the FC. You should search and read some threads about different aftermarket ECU's.

There's also an "Engine Management Forum".

 

figure out who is going to install it and tune it and ask them for their recommendations.