I just sold an 06 3900 to a friend whos replacing his 2.8 in a fiero.
he will more than double his HP stock and torque curve is almost flat from 1500-5000.
Bad part is no parts on the 3900 interchange as the bore spacing was increased slightly.
But its a real strong 60* motor and cheap enough to look at replacing your entire 3.4.
As for souping up the 3.4,it would be cheaper to look for a 95+ with a 3800.
http://forum.camarov6.com/index.php
www.fullthrottlev6.com