The difference between the SH (Super Handling) and the Base model is ATTS (Active Transfer System) and an LSD in the tranny I think not 100% sure on that. Look for the ATTS towards the driver side of your tranny its a rather unique looking box if it's not there you have a base. The high redline 7400 is from the VTEC engine that gives you that extra high end edge thats all.

I know absolutely nothing about nitrous, can't help ya there bro.