what are the differences in power, reliability, and tunability between the 13bt s4 and s5 and the 13btt i have an 87 turbo and im thinking about a motor swap. also what about 20b, easy to install?

well, i know from experience that a 20b is not the easiest swap, but depending on how you build it, it can have more power than any 13b, but i dont know what it has stock. a s4 TII has around 180hp, a s5 TII has 200hp, and i think 13brew have around 140-150hp, but im not sure about that.

a 13bt would be the easiest swap for a fc, but if you dont mind a lot of wiring, i think a 13brew twin turbo would give you the most power and torque for your money. a 20b will be the most difficult swap, i had to rewire everything and fabricate new motor mounts to make it fit, and i dont really think it was worth it.

so...in my opinion, go with a 13brew with TII drivetrain.