anyone? buller?

they do not exist for the 12 valve engine.

You can get a stand alone SMT-6 or a tec^3 but that will be around 1K and give no immediate hp unless you tune it your self. Very time consumming

what are the possible gains for doing it with proper tuning?

Probly not to much basicly 2.8 should be show cars cause either u got to tear the whole block apart or u are slow.