Carlos,
How many light frames do you have for integration? You might try some of the other pixel rejection algorithms to see if that reduces the noise.
Also, have you tried either AWT or ACDNR for noise reduction? There's a really good description of using AWT from Juan in this thread:
http://pixinsight.com/forum/index.php?topic=3184.0It's aimed at a Luminance image, but the principles apply.
Hope this helps,
Sean