2006 5.0 sx maxes out at 3200 rpm

I have a 94 sx drive with a 2006 replacement 5.0 carberated engine.This engine ran great for 3 seasons and would rev to 4800 rpm's with no problems.This year it wont rev past 3200 rpm's.Ive changed the plugs cap rotor and coil and also rebuilt the 2 barrel carb with no improvement.Ive checked the throtle opening and thats ok .The engine starts ez and is not missing ,it just wont rev.I also notice steam coming from the drive when running but engine temp is 160 and the manifolds and risers are cool to the touch so i dont think its running hot.Im stumped.Can anyone tell me what else to look at ?Thanks