question about test pipe fitment

[2+2white90z32]

i recently picked up a 90 2+2 na auto. the car has an aftermarket cat back but it has a crappy sound. the sound isnt coming from the tail pipe but sounds to be from under the car around the cats. kinda sounds like a damn old farm truck if you lay into it. was looking for some ideas on how to fix this issue and came across the idea of just swapping out for some headers and test pipes to get rid of the 22 year old exhaust. i have no intention on it giving me any hp but just want the car to sound even the slightest bit better. problem ive run into is there isnt much options as far as testpipes for na's. ive found the megan racing units but it says it only fits an m/t. anyone know what keeps it from fitting an auto. ive seen the ones made by specialty z but they dont say anthing about fitting either an auto or manual. didnt know if nissan had two diff cat converter sections with one being for a manual and one being for an auto. dont see any diff in the headers of cat back exhaust. wondering if the autos have a diff bung placement or hangers are in a diff place.

[2+2white90z32]

also i have checked the flanges on the cat back exhaust and its not leaking out the flanges. figured either the cats are clogged or in bad shape and is why its sounding like crap.

[Oh Em Zee]

The difference is that the NA testpipes interfere with the AT transmissions since the bellhousing protrudes further if I recall. It's a fitment issue.
Your problem is likely to be either an open AIV port (look to see if you still have AIV's) http://www.yugobernie.com/plugs.html
or one of the flanges by the cats or mid-section is leaking. Just start the car and crawl down there. You can feather test with a thin piece of paper if you're not super sharp at hearing.

[2+2white90z32]

ive been under it and didn't notice any obvious leaks. Even had a mech look while it was on his lift but he didn't have any ideas. Main reason I'm asking is I can get the area redone by a local muff shop but their wanting 150 to do it. Megan racing units are a bit less and don't have the crimp bends like most muff shops do.

[2+2white90z32]

also I checked out the link for those plugs. Gonna give um a shot to see if that's the problem. Thanks for the help.

[Oh Em Zee]

I know my local place will do it for around $60 for mandrel bent test pipes. $150 seems high.
You might as well just pull the exhaust out and check for rust.