Presumably your speaking about the 2 engine planes, not the ones with a (generally 3rd) rear engine on or near tail somewhere. The exhaust your speaking of is then also noticably smaller in size than those on the engines. It is an exhaust for the generators and supplemental powerclimate control, etc. for the plane. Not for the jet engines for power. Obviously very visible while it's on the ground, where many of these features are running and producing heat/waste gases.
On 3.3L Under hood, center, front engine area, mounted in exhaust manifold. On 3.5L Under hood, center, rear engine area, mounted in exhaust manifold. The 3.3 and 3.5 is engine size.
Under the vehicle mounted between the exhaust manifold and the muffler.
Under hood, driver side, rear engine area, above exhaust pipe flange, mounted in exhaust manifold.
The catalytic converters are in the exhaust pipe that runs under the engine. There are two. Some California models had additional converters mounted to the exhaust manifolds.
Crawl under the vehicle and look up. It is mounted in the exhaust system behind the engine.
Under hood, center, rear engine area, mounted in exhaust manifold
UNDER HOOD, DRIVER SIDE, LOWER ENGINE AREA, BELOW EXHAUST MANIFOLD FLANGE, MOUNTED IN EXHAUST PIPE
UNDER HOOD, DRIVER SIDE, LOWER ENGINE AREA, ABOVE EXHAUST PIPE FLANGE, MOUNTED IN EXHAUST MANIFOLD
Under hood, driver side, rear engine area, below exhaust manifold, mounted in engine block. Under vehicle, driver side, below engine area, between exhaust manifold and transmission bellhousing, mounted front of oil pressure sending unit.
UNDER HOOD, CENTER, REAR ENGINE AREA, MOUNTED IN EXHAUST MANIFOLD
UNDER HOOD, CENTER, REAR ENGINE AREA, ABOVE EXHAUST PIPE FLANGE, MOUNTED IN EXHAUST MANIFOLD.
UNDER HOOD, DRIVER SIDE, LOWER ENGINE AREA, BELOW EXHAUST MANIFOLD FLANGE, MOUNTED IN EXHAUST PIPE.