Not all 92-99 SSEI have the same exhaust set-up. I believe there are at least 3 different arrangements. I spent a long time looking for one for my 93 trying to make something work. I also would have been very happy to have GM sell me one even at their $ (my car had cheap muffler shop one on it falling apart). I ended up custom fitting a Walker OEM replacement F-body muffler on it but am not real happy with the sound.
The catalog books at local parts stores gave the same exception for my car as you have stated above and their pictures for dual outlet mufflers showed both outlets on the same side?? I later found a listing for 93 SSEI at
(strange that Maremont does not list this on their site)
Partsamerica doesn’t list one for a 94 though. I am not 100% sure but I believe the only difference between 93 and 94 arrangement is that the muffler outlet pipes for the 94 have real exhaust tips, whereas 92/93 have pipes that end into heat shields below the rear bumper. Someone else here may be able to confirm.
edit: Link was showing Maremont 1409-11 muffler for 93SSEI & SSE but when I tried again it only comes up for 93SSE supercharged