During my header installation, one of the biggest headaches was the removal of a plate-steel shield that went from the frame to the coach, and from the rear of the tire compartment forward to just about the headlight bucket.

It seems to protect the steering rack and brake booster, but from what I don't know.

I won't detail the PITA it was to get out, but now I am wondering if it serves an important enough purpose to re-install.

Any opinions?

That splash guard is important for air flow for engine cooling, particularly exhausts. There should be one on the right, too. It was added later. 15983041 is the pn. It is pretty easy to make. If you want a picture, PM me with your email address. It is pretty easy to make. Its absence on the right side is the reason for the right side manifold having more stud breaking problems and more ignition wire failures on the right side. Starter heat problems, too.

I just unbolt the left side splash guard in the rear, pull it outward and tie it out of the way with wire while working in there.

The biggest problem I've found with the dreaded plate is access to the brake master cylinder. My wrench buddy didn't figure it was a big deal to remove and replace it, but he works on trucks all day long. He vetoed my suggestion to just leave it off, simply saying it was put there for a reason. Now I know what it was. BTW, a friends Pace has nothing at all in that area, meaning when you look in the wheel well you actually see the engine and all that entails. No protection, and no airflow direction. But then, the only time he drove it further than 40 miles from home the engine blew. He put another 7 G into a coach he payed 17 for and sold it for 3500.