Do I have to remove the intake manifold to replace rear spark plugs on a 1996 nissan maxima?

The intake is two pieces, upper and lower, I assume you are replaceing theknoock senors? In any event here is a link to a video on how to remove the upper intake manifold. 1995 1999 Nissan Maxima Upper intake manifold replacement

this job is not for a newbie. so here we go with instructions. i believe you posted under 2003 nissan maxima section for replacing plugs.
remove engine trim cover that covers manifold and valve cover.
remove ign coils on frt valve cover and remove and install new plugs
for rear bank plugs you would need to remove upper intake plenum. disconnect all necessary electrical connectors and vacuum lines. make sure you are aware where the vacuum hoses go for reinstallation.
remove ign coils on rear bank valve cover. remove and install new plugs.
reassemble all parts.

What engine do you have in your Nissan that has the misfire, how many cylinders and how many liters???

This is possibly true, especially if you have a 6 cylinder. They don't actually remove the whole intake from the motor, there is a section of the intake system that can be removed fairly easily and then the plugs can be accessed. Unfortunately, this design was more to push the price of a tune up higher than a needed design change, at least in my opinion. Since you have to remove that part most people are more inclined to take a vehicle to the dealer to replace spark plugs instead of doing it themselves and as you know, the dealership prices are higher than anywhere else and the mechanics have the same qualifications other mechanics have.Typically no seals need to be replaced when this is done but it does take more time and that is where the dealership makes it's money.

http://www.ehow.com/how_6523412_replace-spark-plugs-1995-maxima.html
There are the steps to replace the plugs. You shouldn't need to remove the manifold.
Thanks,
Lee

its easy my friend, take your tools, drain engine oil and coolant, remove left side rocker ornament and air duct of intake manifold, collector,hose wires, harness etc, remove ignition coils, egr tube,intake manifold collector supports and the manifold( right cylinder head only,) remove intake manifold, and replace knock sensor to avoid some trouble in the future

For the 3 spark plugs in front:
1. You would have to remove the plastic protective cover (this cover is silver&red w/ the words "nissan and v6 3000")
2. unplug connector and remove coil (DO NOT mix up the coils, keep the same coils on the same cylinder)
3. Remove spark plug

Rear 3 plugs: located on the rear of the intake (the black pipes atop the engine). there are 3 openings at the rear of the black intake pipes, each opening has a coil mounted.
1. Unplug coil connector and remove coil
2. remove spark plug (you'll need a long extension)
***Installation is reverse, be sure not to over tighten the plugs!! Use anti-seize compound on all the new plugs threading. Hopefully this helps!!

The first 3 plugs are on the top of the forward valve cover. The back 3 are under the intake manifold.

You will have to remove the upper intake manifold to replace the rear plug.There are no shortcuts ,and besure to replace the upper intake gasket as well.

that sounds like you have a clogged exaust porton either the intake manifold or the exaust manifold.