True duals with flowmasters is to much exhaust for that engine, bigger is not always better when dealing with exhaust on gas engines.
Look up the term "exhaust scavenging" this should give you some insight on why not to use thay much exhaust, unless you plan on using wot all the time.
I never had to recal my maf after the new pulley, just make sure your intake can handle a larger volume of air, better intake piping and a larger volume air filter will go a long ways.
I stayed away from nitrous, its hard on an engine, superchargers are hard on an engine, from watching other use this combination I know its a quick way to wear the engine out.
How many miles do ypu want before rebuild/replacement?
Even normally aspirated engines can have a hard time handling nitrous at times.