If anyone owns a 1995-1997 Tacoma 4WD 2.7L regular cab with the original Toyota catalytic converter, please keep reading. This may apply to later years also. These are the short 4WD trucks with a single cat vs. Xtra cabs which apparently have two.
Look underneath the truck where the cat is installed above the cross-member on the passenger side. There are rows of ventilation holes on the bottom of the cat. At one end, there should be a single ventilation hole in the center in its own final row. I'm trying to find out whether that hole is on the muffler (outlet) side or engine (intake) side of the cat, as properly installed. I'm not sure if they all have that feature but it makes a quick reference.
These cats are also asymmetrical in that one end has a longer expanse of "unbent" sheet metal with longer stiffener ribs. The gaskets at each end are the same, which is confusing if you have no reference to the old one (long story).
The factory manual has a weak diagram, with reference to a "delta mark" at the intake end; absent on the factory replacement. It seems many of these factory cats are poorly marked for directionality. The cat needs to be installed in the right direction because two chemical reactions augment each other. It affects emissions but is negligible to flow.
Thanks for any help, especially if you can post a photo somewhere.
Vic