Will the Apex'i Dunk-styled Staight-Thru design Muffler bolt on to the factory equipment or is welding required? Also what does the Apex'i AFC module do? What hp gains can I expect? Is there a better high-flow muffler out there for the Maxima? Thanks for answers.......

Unless it's designed for the Maxima>>>
 

it'll require some welding. If it's designed for it, it will "bolt" on in place of the muffler like how the Stillen muffler or HKS muffler section only is.

nice picture :)

S-AFC allows adjustment of the fuel curve. Will gain a few HP, but it also has a use as a safety device on the track (aka allowing you to run richer to avoid blowing up! :)).