On a side note I've been following this thread. Here are plausible solutions to the problems:

1) rusting in general:
-Painting the rails after installation with rust resistant paint
-Undercoat the body around the rails and the rails themselves after installation
-Do both

2) Caps or no Caps
-If capped, small holes should be drilled at mentioned above because they most likely will not be "air" tight.
-If uber worried about rusing with caps drill holes and install small upward facing pipe to avoid water intoduction while allowing the hole for moistrue evapuration.
-If uncapped, probably should drill holes alot bottom for drainage as water/dirt/road salt will get into the rails
- Also regular maintance and ensuring dirt/road salt is not sitting inside the rails will prevent the worse corrsion.

thats my 0.02.


1998 SE Duratec V6 ATX Ebay intake with K&N Filter Trubendz Exhaust Custom Hood