Mike actually the up pipes aren't in the way of the banjo bolts. And yes you could pull banjo bolts to do injectors and I do believe some do and some guys don't pull them when installing injectors.
Robin I really don't think you would see an increase in fuel pressure but if there is any actual increase with this modd I would think it would be in gph of flow that you would see an increase. The only real experience I have with increasing size to fuel is in marine. And when going with going from a single carb to a blower with dual carb you need to go from 3/8 line to a 1/2 lines at 4-8psi. And you can NOT increase fuel pressure over 8psi due to the needle & seat in the carb. Because with a 3/8 line dual carbs at 4-8psi you get a lean condition. I know it is totally different in a 7.3 diesel but any increase in size will let you increase gph. So to truely test this modd I would love to see the #'s on gph of flow at wot.
This is a photo of the Early banjo bolt modded to 7/32. Now I have seen where guys go with 1/4" and I personally feel that size weakens the bolt shaft.
Also here is a photo of the two different style banjo bolts the 7.3 has. The modded bolt on the right is out of a Early99 and the unmodded bolt is out of a 02 courtesy of Larrythe handyman "Thanks Larry " Just incase you go to replace the oring there are 2 different orings. Bob/ Diesel Orings has both. Also I did end up modded the late model bolt too but you can only go about 5/32 without getting into the longer shank on the bolt and I felt it was a better modd.
Now I did this not because I am in search of huge hp#'s or because I thought I would see or feel any improvement but because I felt it can't hurt to make it easier for the fuel to get to the injectors. Besides I was replacing the orings anyways.
Now the Strickly Diesel banjo bolts have alot more going for them other than increasing flow. They are made out of SS and use a copper washers instead fo STUPID orings. 7.3L Banjo Bolt Kit