These are all good ideas but I think folks are over-engineering, and over-thinking things a bit. To clarify what I mean I will go ahead and post the instructions, materials list, and pictures for the DWV intake. It really is about as simple and as easy as it gets, no grinding, no fitting, no painiting. Once Bill posts the write up I sent him I will edit this to comply with his wishes. See below:
DWV intake mod for the 2004-2008 F150 with 5.4L engine
Materials:
1. 7.5 inch length of 3 inch inside diameter black ABS DWV pipe.
2. One female-to-female 3 inch black ABS coupler.
3. One rubber downspout connector from the plumbing section of Lowes or Home Depot.
4. One 4 inch stainless steel worm clamp.
5. Small container of ABS pipe glue.
Assembly:
1. Cut black ABS pipe to length and remove any burrs from the ends.
2. Apply a light coat of ABS pipe glue to the end of the black ABS DWV pipe in a one inch wide strip. Apply a light coat of ABS glue to the inside of one end of the female coupler and immediately press the coupler into the black ABS DWV pipe with a twisting motion to fully seat the pipe into the coupler. Allow to dry 30 minutes.
3. Attach rubber downspout connector over end of female coupler and seat fully.
Installation:
1. Remove stock intake tube by removing 10mm bolt holding it in place.
2. Using a large flat blade screwdriver, insert it in the joint at the end of the flex section on the bottom where the notch is in order to remove the snorkel. Spraying silicone lubricant or WD-40 in the joint will help it come out easily. Be careful not to damage the flex section or snorkel in case you need to return to stock.
3. Loosen 4 inch stainless steel worm clamp and slip over end of flex section. Tighten the worm clamp enough that it will not fall off.
4. Insert the end of the 3 inch black ABS DWV pipe into the flex section of the intake and slide it into the flex section as far as it will go.
5. Reinstall stock intake tube and replace 10mm bolt.
6. Slide the 3 inch black ABS DWV pipe out of the flex section and seat the downspout adapter in the fender hole while compressing the flex section.
7. While holding the flex section compressed, tighten the stainless steel worm clamp to hold the black ABS DWV pipe in place.
IMPORTANT: If the flex section is not compressed the DWV intake mod may vibrate or rattle.
Pictures:
Ingredients for the DWV intake mod
Finished DWV intake mod
No restrictions here! Full 3 inch diameter end to end.
Additional pictures are in my gallery.