fuel pressure?

[magicman2400]

OK! here we go , short and simple.. Ford 03 psd 6.0 305k, no oil loss , no coolant loss . misses , skipps, sluggish at 2k ish on the h-way.heres the trick... turn right and all 8 cyls go good and if your not careful you could burn off the remaining good rubber I have on the rear end.. Thats the good part. Turn left and you have mabey 4 cyls at best and a skeeter cloud from the s#1^ pipe. other than that I get about 6 to 7 cyl's running norm... anyone got a clue?

facts:

new filters.. oil and fuel
drained water
no leaks
tank cond. full or empty
no codes... ever!!
new battery's and cables to the starter and alt.
new alt (stock)

fuel system flush from one end to the other?
this came on slowly
no change