dvkim,
Yes, and yes! I'm not sure if by "exhaust" you mean just the muffler or the whole system, but in either case the '97+ exhaust on the 3.2 liter motors is less restrictive than the one used on the original 3.0 engines. As I'm sure you've read on the FAQ, the main difference between the two exhaust systems lies in the fact that the 3.2 liter engines come from the factory with headers instead of an iron manifold. In addition to the larger displacement, this improvement in the exhaust system is one of the reasons that the 3.2 engine makes more power than the 3.0.
Your post caught my attention because I have upgraded my '91 to a stock 3.2 exhaust system (except for the catalytic converters).
I added the 3.2 liter muffler first because a) my original one had a dent in the bottom from the previous owner, b) I didn't care for the looks of the oval exhaust tips, and c) the newer muffler is painted a dull black color on the bottom at the factory which helps it blend into the back of the car better than the older muffler. The newer muffler I put on my car came off of a '97 (or '98, I can't remember) and installed without any trouble (just bolted right up). I wasn't really expecting any performance gain from it, but after installing it, I was pleasantly surprised to find that a) it has a slightly deeper sound to it, especially at lower RPMs and b) the throttle response and eagerness of the car to accelerate seemed noticeably improved. I've never dynoed my car, so I don't have any numbers to share, but it definitely "felt" better.
Later, I managed to come across a set of factory 3.2 liter headers from a ’00 NSX and put these on the car. I decided to go with the factory headers because, though some of the aftermarket headers may make more power than the factory headers, they also cost quite a bit more. The factory 3.2 headers installed on my car without any trouble, but two significant modifications were required to make them fit and work. The first obstacle (the hard one) lies in the fact that the circular shaped flange with two bolt holes on the header pipe (after the collector) won’t match up to the rounded triangular flange with three bolt holes (duh!) on the old style exhaust pipes. To make it fit, the new style flange was cut off of the end of the headers and an old style one was welded on (with the appropriate length of piping): voila, fitment problem solved. The second obstacle (the easy one) was the fact that the location of the O2 sensors on the headers is slightly different than that of the original exhaust manifolds. To make it work, the O2 sensor wires just had to be extended by a small amount so that the sensor could reach the new location. Once that was accomplished, the original O2 sensors plugged into the headers without any issue.
The performance difference from the factory headers was much more significant than that of the muffler. The car got a nice little bump in power, throttle response and eagerness to rev seemed improved yet again over just the muffler, and though I wouldn’t say it’s that much louder, the engine note seemed to take on a more “pronounced” sound… It’s hard to describe, but it just sounds fuller or richer and definitely better! Again, I don’t have any dyno numbers to share, just what I felt happen with the car.
So that’s been my experience with the two exhausts… hope this helps answer your question!